As filed with the Securities and Exchange Commission on December 4, 2017March 13, 2019

RegistrationNo. 333-221588333-229913

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

PRE-EFFECTIVE AMENDMENT NO. 1

TO

FORMS-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

GLACIER BANCORP, INC.

(Exact name of registrant as specified in its charter)

49 Commons Loop, Kalispell, Montana 59901 (406)756-4200

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

RANDALL M. CHESLER

President and Chief Executive Officer

49 Commons Loop

Kalispell, Montana 59901

(406)756-4200

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies of communications to:

Approximate date of commencement of proposed sale of securities to the public:

As soon as practicable after this Registration Statement becomes effective and upon completion of the merger described in the enclosed document.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box.  ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, anon-accelerated filer, a smaller reporting company, or an emerging growth company. See definition of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule12b-2 of the Exchange Act. (Check one):

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided purchase to Section 7(a)(2)(B) of the Securities Act.  ☐

Information contained herein is subject to completion or amendment. A registration statement relating to these securities has been filed with the Securities and Exchange Commission. These securities may not be sold prior to the time the registration statement becomes effective. This document shall not constitute an offer to sell nor shall there be any sale of these securities in any jurisdiction in which such offer or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.

PRELIMINARY—SUBJECT TO COMPLETION—DATED DECEMBER 4, 2017MARCH 13, 2019

MERGER PROPOSED – YOUR VOTE IS VERY IMPORTANT

Dear Inter-Mountain Bancorp., Inc.FNB Bancorp Shareholders:

As you may know, the boards of directors of Inter-Mountain Bancorp., Inc.FNB Bancorp (“IMB”FNB”) and Glacier Bancorp, Inc., Kalispell, Montana (“Glacier”) have each unanimously approved a merger of IMBFNB with and into Glacier, subject to approval by IMBFNB shareholders and appropriate bank regulators. Immediately following the merger, IMB’sFNB’s subsidiary The First SecurityNational Bank (“FSB”of Layton (the “Bank”) will be merged into Glacier’s subsidiary Glacier Bank (“Glacier Bank”), subject to approval of appropriate bank regulators.

Under the terms of the Plan and Agreement of Merger, dated October 26, 2017January 16, 2019 (the “merger agreement”), each outstanding share of IMBFNB common stock will be exchanged for 22.8410.6474 shares of Glacier common stock, subject to certain adjustments.

The amount of Glacier common stock exchanged for each share of IMBFNB common stock is subject to adjustment in the event that the average closing price for Glacier common stock over a20-day period prior to closing calculated in accordance with the merger agreement, is more than $46.63 or less than $28.07$32.44, or less than $34.47, if such stock price has also declined by ten percentage points more than $42.11, and IMBthe KBW Regional Bank Index. In that event either Glacier or Glacier providesFNB, respectively, may provide notice to terminate the merger agreement, andprovided that the merger agreement will not be terminated if either FNB or Glacier, or IMB, as the case may be, elects to adjust the number of shares on aper-share basis to be issued in the merger (or, with respect toas described in this proxy statement/prospectus. Glacier electsmay also elect to pay additional cash consideration as described in this proxy statement/prospectus)lieu of increasing the number of shares to be issued in order to avoid such termination.the merger.

The merger agreement establishes a minimum requirement for IMB’sFNB’s capital ($73,500,000)39,285,000) prior to the closing of the merger. If IMB’sFNB’s closing capital, asafter being adjusted in accordance with the terms of the merger agreement to take into account any transaction expenses in excess of amounts permitted under the merger agreement, is in excess of the minimum required, IMBFNB may in its sole discretion pay a special dividend to its shareholders in the amount of such excess. For purposes of illustration only, as of October 31, 2017, IMB’sIf FNB’s closing capital would have been approximately $75.3 million, resulting in a special dividend available to IMB’s shareholders of approximately $1.8 million inis less than the aggregate or approximately $8.70 per share. Accordingly, based onminimum required, the above, it is presently anticipated that a special cash dividendtotal Glacier stock consideration will be paid immediately priorreduced by a number of shares equal in value to closing.the difference between the required amount of FNB closing capital and the amount of the actual FNB closing capital, as adjusted.

Assuming for purposes of illustration only that the average closing price for Glacier common stock is $40.05,$41.06, which was the closing price of Glacier common stock on November 30, 2017March 11, 2019, as quoted on the NASDAQ Global Select Market, and that there is no reduction in the exchange ratio due to the FNB closing capital being less than the required amount, for each of your shares of IMBFNB common stock, you will receive 22.8410.6474 Glacier shares with an estimated current value of $914.78. Trading in IMB common stock occurs very infrequently and is restricted by agreement. During 2017, IMB is aware of two transactions in its common stock, each of which was valued at $480.76 per share.$26.58.

Assuming the exchange of all outstanding IMBFNB common stock for Glacier common stock in accordance with the merger agreement, IMBFNB shareholders will, in the aggregate, own approximately 5.51%2.36% of Glacier’s outstanding common stock following the merger.

FNB will hold a special shareholders’ meeting to vote on the merger agreement.The special meeting of the shareholders of IMB will be heldagreement on January 16, 2018April 18, 2019, at 1:10:00 p.m.a.m. Mountain Time, inat the Community Room of the First Security Bank branchDavis Conference Center located at 670 19^th Avenue, Bozeman, Montana1651 North 700 West, Layton, Utah59715. 84041. Whether or not you plan to attend the special meeting, please take the time to vote by completing and mailing the enclosed form of proxy.

The board of directors of IMBFNB has unanimously recommended that you vote FOR approval of the merger agreement and the other proposals described in this proxy statement/prospectus.

Neither the Federal Deposit Insurance Corporation, Securities and Exchange Commission, nor any state securities commission has approved the securities to be issued by Glacier or determined if this proxy statement/prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The shares of Glacier common stock to be issued in the merger are not savings or deposit accounts or other obligations of a bank and are not insured by the Federal Deposit Insurance Corporation, the Federal Deposit Insurance Fund or any other governmental agency. Such shares are not guaranteed by Glacier or IMBFNB and are subject to investment risk, including the possible loss of principal.

This proxy statement/prospectus is dated December 4, 2017March 13, 2019 and is first being mailed to

IMBFNB shareholders on or about December 7, 2017.March 15, 2019.

INTER-MOUNTAIN BANCORP., INC.FNB BANCORP

208 East12 South Main Street

Bozeman, Montana 59715Layton Utah 84041

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

TO BE HELD January 16, 2018APRIL 18, 2019

TO THE SHAREHOLDERS OF INTER-MOUNTAIN BANCORP., INC.FNB BANCORP:

A special meeting of shareholders of Inter-Mountain Bancorp., Inc.FNB Bancorp (“IMB”FNB”) will be held onJanuary 16, 2018 April 18, 2019, at1: 10:00 p.m.a.m. Mountain Time,in at theCommunity Room of the First Security Bank branch Davis Conference Center located at 670 19^th Avenue,Bozeman, Montana59715.The1651 North 700 West, Layton, Utah 84041. The special meeting is for the following purposes:

Holders of record of IMBFNB common stock at the close of business on December 1, 2017,March 6, 2019, the record date for the special meeting, are entitled to notice of, and to vote at, the special meeting or any adjournments or postponements of it. The affirmative vote of the holders of at leasttwo-thirds (66 2/3%) a majority of the shares of IMB’sFNB’s outstanding common stock is required for approval of the merger agreement. To that end, IMB’sFNB’s directors and certain IMB shareholdersexecutive officers have signed agreements to vote their shares in favor of the merger agreement. Such persons are entitled to vote 120,5301,357,605 shares representing approximately 59.15%42.95% of all outstanding shares of IMBFNB common stock. As of December 1, 2017,March 6, 2019, there were 203,7633,160,969 shares of IMBFNB common stock outstanding.

IMBFNB shareholders have the right to dissent from the merger and obtain payment of the fair valueof their shares of IMBFNB common stock under the Montana Code Annotated,Utah Revised Business Corporations Act (“URBCA”), Sections35-1-826 1301 through35-1-839. 1331. A copy of the provisions regarding dissenters’ rights is attached asAppendix B to the accompanying proxy statement/prospectus. For details of your dissenters’ rights and how to exercise them, please see the discussion under “The Merger – Dissenters’ Rights of Appraisal.Rights.”

Your vote is important. Whether or not you plan to attend the special meeting, please complete, sign, date and promptly return the accompanying proxy using the enclosed envelope. If for any reason you should desire to revoke your proxy, you may do so at any time before it is voted at the meeting.If you do not vote your shares, it will have the same effect as voting against the merger.

The board of directors of IMBFNB has determined that the merger agreement is fair to, advisable, and in the best interests of IMBFNB and its shareholders and unanimously recommends that you vote FOR approval of the merger agreement. With regard to its recommendation that shareholders vote FOR approval of the merger agreement, the board of directors of IMBFNB considered a number of factors, including the receipt of a fairness opinion from the investment banking firm of ProBank Austin, as discussed in “ Background of and Reasons for the Merger” beginning on page 19.18. Such factors also constituted the reasons that the board of directors determined to approve the merger agreement and to recommend that IMBFNB shareholders vote in favor of the merger agreement.

You will receive instructions on how to exchange your shares of IMBFNB common stock for the merger consideration promptly after the closing of the merger.

Bozeman, MontanaLayton, Utah

December 4, 2017March 13, 2019

WHERE YOU CAN FIND MOREREFERENCES TO ADDITIONAL INFORMATION ABOUT GLACIER

Glacier

This proxy statement/prospectus incorporates important business and financial information about Glacier from documents that wereGlacier has previously filed with the SEC that are not included in or delivered with this document. See “Documents Incorporated by Reference” elsewhere in this document.

Glacier files annual, quarterly and current reports, proxy statements, and other information with the Securities and Exchange Commission (“SEC”). You may read and copy any reports, statements,that are contained in or other information that Glacier files with the SEC at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at1-800-SEC-0330 for further information on the operation of the Public Reference Room. Glacier’s SEC filings are also available to the public on the SEC site (http://www.sec.gov). As described below, you may also obtain the documents that Glacier is incorporatingincorporated by reference into this proxy statement/prospectus from Glacier.

Glacier has filedprospectus. For a Registration Statement on FormS-4 to register with the SEC the shareslisting of Glacier common stock to be issued to IMB shareholders in the merger. This proxy statement/prospectus is part of that Registration Statement and constitutes a prospectus of Glacier in addition to being a proxy statement of IMB for its special shareholders meeting. As allowed by SEC rules, this proxy statement/prospectus does not contain all of the information that you can find in the Registration Statement or the exhibits to the Registration Statement.

You can obtain the documents that are incorporated by reference into this proxy statement/prospectus, through Glacier orplease see the SEC.section entitled “Where You can obtainCan Find More Information.” This information is available for you to review at the SEC’s website athttp://www.sec.gov.

You may request copies of this proxy statement/prospectus and any of the documents from the SEC, as described above. These documents are also available fromincorporated by reference into this proxy statement/prospectus or other information concerning Glacier, without charge, excluding exhibits unless Glacier has specifically incorporated such exhibits by reference in this proxy statement/prospectus, by requesting them in writing or by telephone from Glacier at the following address:or written request directed to:

Glacier Bancorp, Inc.

49 Commons Loop

Kalispell, Montana 59901

ATTN: Ron Copher, Corporate Secretary

Telephone: (406)751-7706

Certain reports can also be found on Glacier’s website atwww.glacierbancorp.com.

Glacier’s common stock is traded on the NASDAQ Global Select Market under the symbol “GBCI.”

You will not be charged for the documents that you request.If you would like to request documents, please do so by January 5, 2018April 11, 2019 in order to receive them before the IMBFNB special shareholders’ meeting.

Glacier’s common stockFNB

FNB does not have a class of securities registered under Section 12 of the Securities Exchange Act of 1934 (the “Exchange Act”), is traded onnot subject to the NASDAQ Global Select Market underreporting requirements of Section 13(a) or 15(d) of the symbol “GBCI.”Exchange Act, and accordingly does not file documents or reports with the SEC.

If you have questions concerning the merger or this proxy statement/prospectus, would like additional copies of this proxy statement/prospectus, would like copies of FNB’s articles of incorporation or bylaws, or would like copies of FNB’s historical consolidated financial statements or need help voting your shares, please contact:

FNB Bancorp

12 South Main

Layton, Utah 84041

ATTN: Nic Bement

(801)813-1600

TABLE OF CONTENTS

i

QUESTIONS AND ANSWERS

Why am I receiving these materials?

We are sending you these materials to solicit your proxy to vote in favor of the merger and to help you decide how to vote your shares of Inter-Mountain Bancorp., Inc.FNB Bancorp (“IMB”FNB”) common stock with respect to its proposed merger with Glacier Bancorp, Inc. (“Glacier”). The merger cannot be completed unless IMBFNB receives the affirmative vote of the holders of at leasttwo-thirds (66 2/3%) a majority of the outstanding shares of IMB’sFNB’s common stock. IMBFNB is holding a special meeting of shareholders to vote on proposals relating to the merger. Information about the special meeting is contained in this document. See “IMB“FNB Special Shareholders Meeting.”

This document is both a proxy statement of IMBFNB and a prospectus of Glacier. It is a proxy statement because the officers and board of directors of IMBFNB (the “IMB“FNB Board”) are soliciting proxies from IMBFNB shareholders in connection with voting on the merger. It is a prospectus because Glacier will issue shares of its common stock in exchange for shares of IMBFNB common stock as consideration to be paid in the merger.

What will IMBFNB shareholders receive in the merger?

Under the terms of the merger agreement, each share of IMBFNB common stock will be exchanged for 22.8410.6474 shares of Glacier common stock, subject to adjustment as described below.

Assuming for purposes of illustration only that the exchange of all outstanding IMB common stockaverage closing price for Glacier common stock in accordance withis $41.06 (which was the merger agreement, IMB shareholders will own,closing price for Glacier common stock on March 11, 2019), and that there is no reduction in the aggregate, approximately 5.51%exchange ratio due to the FNB Closing Capital (discussed below) being less than the required amount, each share of Glacier’s outstandingFNB common stock following the merger.would be exchanged for Glacier common stock with a total value equal to $26.58.

If the IMBFNB Closing Capital (as defined in the merger agreement) exceeds $73,500,000,$39,285,000, subject to certain adjustments, IMBFNB may, upon written notice to Glacier and effective immediately prior to the closing of the merger, declare and pay a special dividend to its shareholders in the amount of such excess.

If the FNB Closing Capital is less than $39,285,000, the total number of Glacier shares issued in the merger will be reduced by a number of shares equal in value to the differential between $39,285,000 and the actual FNB Closing Capital.

The amount of Glacier common stock exchanged for each share of IMBFNB common stock may also be adjusted in certain circumstances based on whetherif Glacier common stock is trading either higher or lower than prices specified in the merger agreement immediately prior to the closing of the merger, in order to avoid termination of the merger agreement.agreement as follows:

On November 30, 2017, the closing price of Glacier’s common stock was $40.05 per share.

On March 11, 2019, the closing price of Glacier common stock was $41.06 per share.

By voting to approve the merger agreement, IMBFNB shareholders will give the IMBFNB Board the authority to elect to cause IMBFNB to accept a reduction on aper-share basis of the number of shares of Glacier common stock to be issued in the merger if the Glacier average closing price exceeds $42.11$46.63 as described above. See “The Merger – Termination of the Merger Agreement.”

What will I receive inAssuming the merger?

Eachexchange of all outstanding share of IMBFNB common stock you own will be exchanged for 22.841 shares of Glacier common stock, subject to adjustment as described above.

Assuming for purposes of illustration only that the average closing price for Glacier common stock is $40.05 (which wasin accordance with the closing price for Glaciermerger agreement, FNB shareholders will own, in the aggregate, approximately 2.36% of Glacier’s outstanding common stock on November 30, 2017), each share of IMB common stock would be exchanged for consideration with a total value equal to $914.78.following the merger.

How soon after the merger is completed can I expect to receive my merger consideration?

Glacier will work with its exchange agent, American Stock Transfer & Trust Company, LLC, to distribute consideration payable in the merger as promptly as practicable following the completion of the merger.

Will the shares of Glacier common stock that I receive in the merger be freely transferable?

Yes. The Glacier common stock issued in the merger will be transferable free of restrictions under federal and state securities laws.

When will the merger occur?

We presently expect to complete the merger during the firstsecond quarter of 2018.2019. The actual timing of the transaction is subject to a number of factors (primarily regulatory approvals), many of which are beyond the control of Glacier and IMB.FNB. The merger is also conditioned upon and will occur after the approval of the merger agreement by the affirmative vote of holders of at leasttwo-thirds (66 2/3%) a majority of the shares of IMBFNB common stock, after the merger has received regulatory approvals, and following the satisfaction or waiver of the other conditions to the merger described in the merger agreement and summarizesummarized under “The Merger” below.

If the merger does not occur by July 31, 2018,September 30, 2019, either Glacier or IMBFNB may unilaterally terminate the merger agreement. However, if as of July 31, 2018,September 30, 2019, the condition to closing that all required governmental regulatory approvals have been obtained has not been satisfied, then the deadline for closing of the merger will be extended to on or before October 31, 2018,November 30, 2019, if Glacier notifies IMBFNB in writing on or prior to July 31, 2018September 30, 2019 of its election to extend such closing deadline.

When and where will the special meeting take place?

IMBFNB will hold a special meeting of its shareholders on January 16, 2018April 18, 2019, at 1:10:00 p.m.a.m. Mountain Time, inat the Community Room of the First Security Bank branchDavis Conference Center located at 670 19^th Avenue, Bozeman, Montana 59715.1651 North 700 West, Layton, Utah 84041.

Who may vote at the special meeting?

The IMBFNB Board has set December 1, 2017March 6, 2019 as the record date for the special meeting. If you were the owner of IMBFNB common stock at the close of business on December 1, 2017,March 6, 2019, you may vote at the special meeting.

What vote is required to approve the merger agreement?

Approval of the merger agreement requires the affirmative vote of the holders of at leasttwo-thirds (66 2/3%) a majority of the shares of IMB’sFNB’s outstanding common stock. As described in this proxy statement, IMB’sFNB’s directors and certain IMB shareholdersexecutive officers have agreed to vote the shares they are entitled to vote in favor of the merger agreement. As of the date hereof, such persons are entitled to vote 120,5301,357,605 shares of IMBFNB common stock, representing approximately 59.15%42.95% of all outstanding shares of IMBFNB common stock. See “IMB“FNB Special Shareholders’ Meeting” and “The Merger – Voting Agreements.Agreement.”

What vote is required to approve the adjournment of the special meeting, if necessary or appropriate?

If less than a quorum is represented at the special meeting, a majority of the shares so represented may adjourn the special meeting without further notice. The proposal to adjourn the special meeting, if necessary or appropriate, including adjournments to solicit additional proxies, will be approved if the votes cast in favor of the proposal exceed the votes cast against the proposal, assuming a quorum is present. If less than a quorum is represented at the special meeting, a majority of the shares so represented may adjourn the meeting without further notice.

How do I vote?

If you were a shareholder of record on December 1, 2017,March 6, 2019, you may vote on the proposals presented at the special meeting in person or by proxy. We urge you to vote promptly by completing the enclosed proxy card. Even if you plan to attend the special meeting, we recommend that you vote your shares in advance as described below so that your vote will be counted if you later decide not to attend the special meeting.

You may cast your vote by mail by completing, signing and dating the enclosed proxy card and returning it to us promptly in the enclosed envelope. Returning the proxy card will not affect your right to attend the special meeting and vote.

If you choose to vote your shares in person at the special meeting, please bring the enclosed proxy card and proof of identification.

Can I change my vote after I have mailed my signed proxy card?

Yes. You may change your vote at any time before your proxy is voted at the special meeting. If your shares of IMBFNB common stock are held in your own name, you may change your vote as follows:

If you choose either the first or second method above, you must submit your notice of revocation or your new proxy card to IMB’sFNB’s Secretary prior to the vote at the special meeting.

What happens if I return my proxy but do not indicate how to vote my shares?

If you sign and return your proxy card but do not provide instructions on how to vote your shares of IMBFNB common stock at the special meeting of shareholders, your shares of IMBFNB common stock will be voted “FOR” approval of the merger agreement and “FOR” approval of one or more adjournments of the special meeting.

How does the IMBFNB Board recommend that I vote?

The IMBFNB Board unanimously recommends that IMBFNB shareholders vote “FOR” the proposals described in this proxy statement/prospectus, including in favor of approval of the merger agreement.

What do I need to do now?

We encourage you to read this proxy statement/prospectus and related information in its entirety. Important information is presented in greater detail elsewhere in this document, and documents governing the merger are attached as appendices to this proxy statement/prospectus. In addition, much of the business and financial information about Glacier that may be important to you is incorporated by reference into this document from documents separately filed by Glacier with the Securities and Exchange Commission (“SEC”). This means that important disclosure obligations to you are satisfied by referring you to one or more documents separately filed with the SEC.

Following review of this proxy statement/prospectus,please complete, sign, and date the enclosed proxy card and return it in the enclosed envelopeas soon as possible so that your shares of IMBFNB common stock can be voted at IMB’sFNB’s special meeting of shareholders.

Should I send in my common stock certificates now?

No.Please do not send your IMBFNB common stock certificates with your proxy card. You will receive written instructions from Glacier’s exchange agent promptly following the closing of the merger on how to exchange your IMBFNB common stock certificates for the merger consideration.

What risks should I consider?

You should review carefully our discussion under “Risk Factors.” You should also review the factors considered by the IMBFNB Board in approving the merger agreement. See “Background of and Reasons for the Merger.”

What are the material United States federal income tax consequences of the merger to me?FNB shareholders?

Glacier and IMBFNB expect to report the merger of IMBFNB with and into Glacier and the merger of FSB with and into Glacier Bank as one or moreatax-free reorganizationsreorganization for U.S. federal income tax purposes under Section 368(a) of the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). In connection withIt is a condition to the filingclosing of the registration statement of which this document is a part, Garlington, Lohnmerger that Miller Nash Graham & Robinson PLLP, specialDunn LLP, tax counsel to Glacier, has delivereddeliver an opinion addressed to Glacier and FNB that the mergersmerger will qualify as one or more reorganizationsa reorganization under Section 368(a).

In atax-free reorganization, a shareholder who exchanges his, her or its shares of common stock in an acquired company for shares of common stock in an acquiring company must generally recognize gain (but not loss) on the exchange in an amount equal to the lesser of (1) the amount of gain realized (i.e., the excess of the sum of the fair market value of the shares of the acquiring company common stock

(including (including any fractional shares) and any cash received pursuant to the merger (excluding any cash received in lieu of fractional shares) over the shareholder’s adjusted tax basis in his, her or its shares of acquired company common stock surrendered pursuant to the merger), or (2) the amount of any cash (excluding any cash received in lieu of fractional shares) received pursuant to the merger.

For a detailed discussion of the material U.S. federal income tax consequences of the merger, see “The Merger – Material U.S. Federal Income Tax Consequences of the Merger.”

We urge you to consult your tax advisor to fully understand the tax consequences to you of the merger. Tax matters are very complicated and in many cases the tax consequences of the merger will depend upon your particular facts and circumstances.

If I do not agree with the merger, doDo I have appraisal or dissenters’ rights?

Yes. If you are an IMBFNB shareholder and you do not agree with the merger, do not vote in favor of the merger agreement, and take certain other actions required by MontanaUtah law, you will have dissenters’ rights under the MontanaUtah Revised Business CorporationCorporations Act, Sections35-1-826 1301 through35-1-839 1331.Exercise of these rights will result in the purchase of your shares of IMBFNB common stock at “fair value,” as determined in accordance with MontanaUtah law. If you elect to exercise this right, we encourage you to consult with your financial and legal advisors. Please read the section entitled “The Merger – Dissenters’ Rights of Appraisal”Rights”for additional information.

Who can help answer my questions?

If you have questions about the merger, the special shareholders meeting, or your proxy, or if you need additional copies of this document or a proxy card, you should contact:

Inter-Mountain Bancorp., Inc.FNB Bancorp

208 East12 South Main Street

Bozeman, Montana 59715Layton, Utah 84041

ATTN: Valarie Abraham,Shelly Holt, Secretary

Tel. No. (406)(801)585-3800831-1600

RISK FACTORS

In addition to the other information contained in or incorporated by reference into this document, including the matters addressed under the caption “Cautionary Note Regarding Forward-Looking Statements,” you should consider the matters described below carefully in determining whether or not to approve the merger agreement and the transactions contemplated by the merger agreement.

Risks Associated with the Proposed Merger

Because you are receiving a fixed number of shares (subject to adjustment) and the market price of the Glacier common stock may fluctuate, you cannot be sure of the value of the shares of Glacier common stock that you will receive.

At the time of the IMBFNB special shareholder meeting, and prior to the closing of the merger, you will not be able to determine the value of the Glacier common stock that you will receive upon completion of the merger. Any change in the market price of Glacier common stock prior to completion of the merger will affect the value of the consideration that IMBFNB shareholders will receive in the merger. Common stock price changes may result from a variety of factors, including but not limited to general market and economic conditions, changes in Glacier’s business, operations and prospects, and regulatory considerations. Many of these factors are beyond the control of Glacier or IMB.FNB. On November 30, 2017,March 11, 2019, the closing price of Glacier common stock was $40.05.$41.06. You should obtain current market prices for Glacier common stock.

The merger agreement provides that the number of shares of Glacier common stock to be issued for each share of IMBFNB common stock in the merger may be decreased or increased, as the case may be, if the average closing price of Glacier common stock, determined pursuant to the merger agreement, is greater than or less than specified prices. If Glacier’s average closing price determined in accordance with the merger agreement is greater than $42.11$46.63 and Glacier elects to terminate the merger agreement, the IMBFNB Board would make the decision,determine, without resoliciting the vote of IMBFNB shareholders, whether or not to accept a decrease on aper-share basis in the number of shares of Glacier common stock to be issued in the merger to avoid such termination. See “The Merger – Termination of the Merger Agreement.”

The merger agreement limits IMB’sFNB’s ability to pursue other transactions and provides for the payment of abreak-up fee if IMBFNB does so.

While the merger agreement is in effect, subject to very narrow exceptions, IMBFNB and its directors, officers, employees, agents and representatives are prohibited from initiating or encouraging inquiries with respect to alternative acquisition proposals. The prohibition limits IMB’sFNB’s ability to seek offers from other potential acquirers that may be superior from a financial point of view to the proposed transaction. If IMBFNB receives an unsolicited proposal from a third party that is superior from a financial point of view to that made by Glacier and the merger agreement is terminated, IMBFNB will be required to pay a $6,500,000$3,200,000break-up fee. This fee makes it less likely that a third party will make an alternative acquisition proposal. See “The Merger –Break-Up Fee.”

Combining our two companies may be more challenging, costly or time-consuming than we expect.

Glacier and IMBFNB have operated and, until the completion of the merger, will continue to operate, independently. Although Glacier has successfully completed numerous mergers in the recent past, this is the largest merger to date and it is possible that the integration of FSBthe Bank into Glacier Bank could result in the loss of key employees, the disruption of the ongoing business of IMBthe Bank or inconsistencies in standards,

controls, procedures and policies that adversely affect our ability to maintain relationships with customers and employees or to achieve the anticipated benefits of the merger. As with any merger of banking institutions, there also may be disruptions that cause us to lose customers or cause customers to take their deposits out of FSB.the Bank.

Unanticipated costs relating to the merger could reduce Glacier’s future earnings per share.

Glacier believes that it has reasonably and conservatively estimated the likely costs of integrating the operations of FSBthe Bank into Glacier Bank, and the incremental costs of operating as a combined financial institution. However, it is possible that unexpected transaction costs or future operating expenses, as well as other types of unanticipated adverse developments, could have a material adverse effect on the results of operations and financial condition of Glacier after the merger. If the merger is completed and unexpected costs are incurred, the merger could have a dilutive effect on Glacier’s earnings per share, meaning earnings per share could be less than they would be if the merger had not been completed.

Glacier has provisions in its articles of incorporation that could impede a takeover of Glacier.

Glacier’s articles contain provisions providing for, among other things, preferred stock and super majority shareholder approval of certain business combinations. Although these provisions were not adopted for the express purpose of preventing or impeding the takeover of Glacier without the approval of Glacier’s board of directors, they may have that effect. Such provisions may prevent you from taking part in a transaction in which you could realize a premium over the current market price of Glacier common stock. See “Comparison of Certain Rights of Holders of Glacier and IMBFNB Common Stock” for a description of Glacier’s potential takeover provisions.

After the merger is completed, IMBFNB shareholders will become Glacier shareholders and will have different rights that may be less advantageous than their current rights.

Upon completion of the merger, IMBFNB shareholders will become Glacier shareholders. Differences in IMB’sFNB’s articles and IMB’sFNB’s bylaws and Glacier’s articles and Glacier’s bylaws will result in changes to the rights of IMBFNB shareholders who become Glacier shareholders. See “Comparison of Certain Rights of Holders of Glacier and IMBFNB Common Stock.”

Risks Associated with Glacier’s Business

Glacier is, and will continue to be, subject to the risks described in Glacier’s Annual Report on Form10-K for the fiscal year ended December 31, 2016, as updated by a Quarterly Report on Form10-Q for the quarter ended September 30, 2017,2018, and subsequent Current Reports on Form8-K, and Quarterly Reports on Form10-Q, all of which are filed with the SEC and incorporated by reference into this proxy statement/prospectus. See “Documents Incorporated by Reference”“References to Additional Information” and “Where You Can Find More Information About Glacier”Information” included elsewhere in this proxy statement/prospectus.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This document, including information included or incorporated by reference in this document may contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include, but are not limited to,(i) statements about the benefits of the merger, including future financial and operating results, cost savings, enhancements to revenue and accretion to reported earnings that may be realized from the merger;(ii) statements about our respective plans, objectives, expectations and intentions and other statements that are not historical facts; and(iii) other statements identified by words such as “expects,” “anticipates,” “intends,” “plans,” “believes,” “seeks,” “estimates,” or words of similar meaning. These forward-looking statements are based on current beliefs and expectations of management and are inherently subject to significant business, economic and competitive uncertainties and contingencies, many of which are beyond Glacier’s and IMB’sFNB’s control. In addition, these forward-looking statements are subject to assumptions with respect to future business strategies and decisions that are subject to change.

In addition to risk factors described above,previously disclosed in Glacier’s reports filed with the SEC relating to risks to Glacier’s business and stock price, and those identified elsewhere in this document (including the section entitled “Risk Factors”), the following potential factors, among others, could cause actual results to differ materially from the anticipated results or other expectations expressed or implied in the forward-looking statements:

Additional factors that could cause actual results to differ materially from those expressed in the forward-looking statements are discussed in Glacier’s reports filed with the SEC.

All subsequent written and oral forward-looking statements concerning the proposed transaction or other matters attributable to Glacier or IMBFNB or any person acting on behalf of Glacier or IMBFNB are expressly qualified in their entirety by the cautionary statements above. Neither Glacier nor IMBFNB undertakes any obligation to update any forward-looking statements to reflect circumstances or events that occur after the date the forward-looking statements are made.

SELECTED HISTORICAL FINANCIAL INFORMATION OF GLACIER

The following table presents selected consolidated financial information of Glacier for the fiscal years ended December 31, 2018, 2017, 2016, 2015, 2014, 2013, and 2012. The consolidated financial data of and for the nine months ended September 30, 2017 and 2016 are derived from unaudited condensed consolidated financial statements, has been prepared on the same basis as the historical information derived from audited financial statements and, in the opinion of Glacier’s management, reflects all adjustments, consisting of normal recurring adjustments, necessary for a fair presentation of this data at or for those dates. The results of operation for the nine months ended September 30, 2017 are not necessarily indicative of the results that may be expected for the entire year ending December 31, 2017.2014. The consolidated financial data below should be read in conjunction with the consolidated financial statements and notes thereto, incorporated by reference in this proxy statement/prospectus. See “Where You Can Find More Information About Glacier.Information.”

COMPARATIVE STOCK PRICE AND DIVIDEND INFORMATION

Glacier Common Stock

Glacier common stock is quoted on The NASDAQ Global Select Market under the symbol “GBCI.” The following table sets forth for the periods indicated:

At October 31, 2017,March 11, 2019, the 78,006,95684,579,372 outstanding shares of Glacier common stock were held by approximately 1,7032,414 holders of record.

IMBFNB Common Stock

IMBFNB common stock is not publicly tradedlisted on a stock market or quoted on any“over-the-counter” market and has been traded only very infrequently. Accordingly, there is no established trading market for FNB common stock. The trades that have occurred have been in accordance with the terms of the Amended and Restated Shareholder Agreement (as subsequently amended, the “Shareholder Agreement”). IMBFNB shares covered by the Shareholder Agreement are generally subject to a right of first refusal of IMBFNB and IMBFNB shareholders other than the proposed transferee. The Shareholder Agreement also prohibits any transfer of IMBFNB shares that would, or with the passage of time would, cause a termination of IMB’sFNB’s election to be subject to subchapter S of the Internal Revenue Code. Upon consummation of the merger, the Shareholder Agreement will be terminated.

IMB receives an annual independent estimated valuation of its outstanding common stock. The following table states the valuation per share of IMB common stock as of December 31 of the year stated:

IMB does not make a market in its common stock and no market exists for its securities. From time to time, IMB becomes aware of transactions in its common stock or redeems shares of its outstanding common stock. IMB is aware of two transactions in its common stock during 2017 involving a total of 127 shares, including 27 shares redeemed by IMB. The price per share for all transactions in 2017 was $480.76 per share.

In 2016, IMB issued 502 shares of its common stock at an issuance price of $398.76 per share. IMB also is aware of 12 other transactions in its common stock in 2016 for a total of 1,335 shares, each at a purchase price of $437.62 per share.

IMBFNB has historically paid dividends on its common stock based upon the estimated tax liability of its shareholders arising from the pass through of IMBFNB income to shareholders under state and federal income tax law. Since the third quarter of 2013, IMBFNB has used an estimated combinedhistorically declared and paid dividends based upon assumed marginal state and federal marginal income tax raterates as well as payout ratios of 45% in declaring dividends each calendar quarter.earnings from operations. Total dividends per share were $19.97 in 2014, $23.05$0.72 in 2015, 0.76 in 2016 and $26.65$1.05 in 2016. For the period ending October 31, 2017, IMB has paid total dividends of $25.07 per share.2017.

At October 31, 2017,March 6, 2019, the 203,7633,160,969 outstanding shares of IMBFNB common stock were held by approximately 126147 holders of record.

IMBFNB SPECIAL SHAREHOLDERS’ MEETING

Date, Time, Place

The IMBFNB special meeting of shareholders will be held on January 16, 2018April 18, 2019, at 1:10:00 p.m.a.m. Mountain Time, inat the Community Room of the First Security Bank branchDavis Conference Center located at 670 19^th Avenue, Bozeman, Montana 59715.1651 North 700 West, Layton, Utah 84041.

As described below under “Votes Required and Quorum,” approval of the merger agreement requires the affirmative vote of at leasttwo-thirds (66 2/3%) a majority of the shares of IMB’sFNB’s outstanding common stock. The proposal to adjourn the special meeting, if necessary or appropriate, including adjournments to solicit additional proxies, will be approved if the votes cast in favor of the proposal exceed the votes cast against the proposal, assuming a quorum is present. If less than a quorum is represented at the special meeting, a majority of the shares so represented may adjourn the special meeting without further notice.

Purpose

At the special meeting, IMBFNB shareholders will:

Record Date; Shares Outstanding and Entitled to Vote

The IMBFNB Board has fixed 5:00 p.m. Mountain Time on December 1, 2017March 6, 2019 as the record date for determining the holders of shares of IMBFNB common stock entitled to notice of and to vote at the special meeting. At the close of business on the record date, there were approximately 126147 holders of record and 203,7633,160,969 shares of IMBFNB common stock issued and outstanding. Holders of record of IMBFNB common stock on the record date are entitled to one vote per share and are also entitled to exercise dissenters’ rights if certain procedures are followed. See “The Merger – Dissenters’ Rights of Appraisal”Rights” andAppendix B.

IMB’sFNB’s directors and certain IMB shareholdersexecutive officers have agreed to vote all shares of IMBFNB common stock they are entitled to vote that are held or controlled by them in favor of approval of the merger agreement. As of the date hereof, a total of 120,5301,357,605 shares of IMBFNB common stock, representing approximately 59.15%42.95% of all outstanding shares of IMBFNB common stock, are covered by the voting agreements.agreement. See “The Merger – Interests of Certain PersonsFNB Directors and Executive Officers in the Merger – Voting Agreements.Agreement.”

Votes Required and Quorum

The affirmative vote of the holders of at leasttwo-thirds (66 2/3%) a majority of the shares of IMB’sFNB’s outstanding common stock is required to approve the merger agreement. At least a majority of the total outstanding shares of IMBFNB common stock must be present, either in person or by proxy, in order to constitute a quorum for the special meeting. For purposes of determining a quorum, abstentions are counted in determining the shares present at a meeting.

For voting purposes, however, shares must be affirmatively votedFOR approval of the merger agreement in order to be counted as votes in favor of the merger. As a result, abstentions with respect to the proposal to approve the merger agreement will have the same effect as votes against such proposal.

If less than a quorum is represented at the special meeting, a majority of the shares so represented may adjourn the special meeting without further notice. The proposal to adjourn the special meeting, if necessary or appropriate, including adjournments to solicit additional proxies, will be approved if the votes cast in favor of the proposal exceed the votes cast against the proposal, assuming a quorum is present.

Voting, Solicitation, and Revocation of Proxies

If the enclosed proxy card is duly executed and received in time for the special meeting, it will be voted in accordance with the instructions given. If the proxy card is duly executed and received but no instructions are given, it is the intention of the persons named in the proxy to vote the shares represented by the proxyFOR the approval of the merger agreement andFOR the proposal to approve one or more adjournments to solicit additional proxies, and in the proxy holder’s discretion on any other matter properly coming before the meeting. Any proxy given by a shareholder may be revoked before its exercise by:

IMBFNB is soliciting the proxy for the special meeting on behalf of the IMBFNB Board. IMBFNB will bear the cost of solicitation of proxies from its shareholders. In addition to using the mail, IMBFNB may solicit proxies by personal interview, telephone, and facsimile. Banks, brokerage houses, other institutions, nominees, and fiduciaries will be requested to forward their proxy soliciting material to their principals and obtain authorization for the execution of proxies. IMBFNB does not expect to pay any compensation for the solicitation of proxies. However, IMBFNB will, upon request, pay the standard charges and expenses of banks, brokerage houses, other institutions, nominees, and fiduciaries for forwarding proxy materials to and obtaining proxies from their principals.

Voting in Person at the Special Meeting

Shares helddirectly in your name as the shareholder of record may be voted in person at the special meeting. If you choose to vote your shares of IMBFNB common stock in person, please bring the enclosed proxy card or proof of identification. Even if you plan to attend the special meeting, we recommend that you vote your shares of IMBFNB common stock in advance as described above so that your vote will be counted if you later decide not to attend the special meeting.

BACKGROUND OF AND REASONS FOR THE MERGER

Background of the Merger

From time to time, over the past several years, the IMBFNB Board with the assistance from time to time of ProBank Austin (“ProBank”),has discussed, analyzed and considered the value and significance of FNB to its shareholders, customers, and employees, as well as the vital role it has played in the local community for over 110 years. In recent years, several bank holding companies have expressed interest in pursuing a combination with FNB, including a merger of equals and an acquisition by a larger institution. As part of its responsibility to consider these expressions of interest, the FNB Board engaged Sandler O’Neill in April of 2014 to provide strategic alternativesadvisory services to enhanceFNB. The FNB Board considered each of the opportunities as they arose, and each time the FNB Board ultimately determined that remaining independent was in the best interests of the shareholders they represented.

Like many other community banks, the FNB Board has strategized around a number of business issues including: increasing competition from bank andnon-bank institutions, continued allowance of regulatory overreach from local credit unions, heightened compliance and regulatory risk, succession planning around an aging management team, and maintaining loan growth in the face of rising real estate lending concentrations. At an FNB Board meeting in May of 2018, President and Chief Executive Officer K. John Jones presented a shareholder value analysis. The FNB Board considered the analysis and achieve future shareholder liquidity. Duringits duty to maximize value for shareholders, as well its responsibility for maintaining the historic legacy of service to the local community, dedicated employees, and the loyal customer base. The FNB Board concluded that time,remaining independent was inmid-2016 and again the best interests of the shareholders but confirmed that that if FNB received a bona fide acquisition proposal that would reasonably be expected to result in a certain value for shareholders, that the FNB Board would need to seriously consider the proposal as an alternative to remaining independent, consistent with its fiduciary duty to the shareholders.

Following the FNB Board’s decision to remain independent, Mr. Jones contacted representatives of Sandler O’Neill in early 2017,July of 2018 and terminated the existing engagement letter.

Later in July of 2018 the Chief Executive Officer of a bank holding company, which we will refer to as PartyCompany A, met with FNB’s Chairman, Kevin Garn, to discuss business opportunities between Company A and FNB. At the meeting, Company A’s Chief Executive Officer expressed his strong interest in acquiring FNB and expressed Company A’s willingness to pay a significant merger premium. Following the meeting, Chairman Garn and Mr. Jones discussed the meeting with representatives of Sandler O’Neill and determined it was likely that Company A would make an acquisition proposal that would meet or exceed the threshold established by the FNB Board at its May 2018 meeting. Accordingly, Chairman Garn and Mr. Jones directed representatives of Sandler O’Neill to contact Company A to try to determine the maximum value that Company A would be willing to offer FNB in an acquisition proposal. As part of this discussion, Chairman Garn, Mr. Jones and representatives of Sandler O’Neill also discussed Glacier and two other potential acquirors and the potential values that they might be willing to offer FNB in an acquisition. Following this conversation, representatives of Sandler O’Neill were instructed to contact Glacier and two other bank holding companies, which we refer to as Company B through its independent financial adviser,and Company C, to gauge their interest in a possible acquisition of FNB.

Throughout August, representatives of Sandler O’Neill held conversations with Glacier, Company A and Company B about the potential acquisition of FNB. Company C had previously expressed interest in exploringacquiring FNB but had now determined that it was not interested in pursuing acquisition discussions with FNB at that time. The conversations with Glacier, Company A and Company B included the sharing of publicly available information along with some high-level guidance on acquisition assumptions. In addition to the conversations with representatives of Sandler O’Neill, each of the companies met with Chairman Garn and Mr. Jones. In these meetings, Chairman Garn and Mr. Jones emphasized that FNB

intended to remain independent, but would seriously consider an acquisition proposal if it met certain criteria. Maximizing value for FNB shareholders was of primary importance, but preserving FNB’s rich legacy, minimizing employee impact, and continuing to support the local community were also important considerations of the FNB Board.

On September 7, 2018 representatives from Glacier met with Chairman Garn, Mr. Jones and other members of the FNB executive team in Layton, Utah.

On September 14, 2018, Company B submitted a potential strategic transaction with ornon-binding letter of intent outlining the proposed terms of an acquisition of IMB. In respectFNB for merger consideration comprised of 75% Company B common stock and 25% cash. At that time, there was no public market for Company B’s common stock, but Company B provided an estimate of the interest expressed by Partyvalue of Company B stock. Company B further indicated that it was not prepared to proceed with a transaction immediately, but expected to be ready to commence due diligence and again with the assistancenegotiation of ProBank,definitive merger documents during the IMB Board engagedfirst quarter of 2019.

On October 10, 2018, Glacier submitted anon-binding letter of intent outlining the principal terms for the proposed acquisition of FNB in formal strategic planning meetings to identify and evaluateexchange for Glacier common stock based on a fixed exchange ratio of 0.5770 Glacier shares in exchange for each share of FNB stock.

Also on October 10, 2018, Company A submitted anon-binding letter of intent outlining the key strategic issues facingprincipal terms for the organization. The first such meetingproposed acquisition of FNB in exchange for Company A common stock, which was held October 18, 2016 and a second was held January 17, 2017.

At these meetings specifically, the IMB Board identified several important planning issues, including existing and anticipated liquidity requests from IMB shareholders, the amount of parent holding company debt and debt service obligations, management and board of director succession at both IMB and FSB, regulatory capital requirements and alternatives for capital formation, and FSB strategic plans for expansion and growth. Notably, the October 2016 meeting included discussions of various capital planning strategies, income tax elections and status, costs and benefits of registration under the United States federal securities laws of IMB securities with the Securities and Exchange Commission, strategic merger alternatives, and potential transactions with publicly traded, bank holding companies.based on a fixed exchange ratio.

In January 2017,Representatives of Sandler O’Neill discussed the IMB Board held its second strategic planning meetingnon-binding letters of intent with Glacier and Company A and Company B, respectively, and provided additional information as requested.

On October 23, 2018, after review of additional information presented, Glacier submitted an updated letter of intent in which it increased the exchange ratio to continue0.6652 Glacier shares in exchange for each share of FNB stock.

On October 28, 2018, the review and discussion of the various strategic issues and alternatives discussed at the October 2016 planning meeting, and to consider other options and alternatives to the extent available.

Then, in late January 2017, IMB’s executive management and ProBank met with executive management of a different bank holding company, which we will refer to as Party C, to discuss a possible strategic merger or other transaction with IMB. Based on these discussions, the strategic alternatives presented by and contemplated with Party C were determined not practicable and discussions terminated.

Following the termination of the discussions with Party C, the IMB Board developed over the next several weeks a strategic plan based in part on decisions made at the strategic planning meetings and in light of its meeting with Party C. The strategic plan outlined the IMB Board’s current decision to maintain IMB’s election to be taxed subject to Subchapter S of the Internal Revenue Code, evaluate changes to the IMB Amended and Restated Shareholder Agreement, continue IMB’s dividend policy of distributing income to its shareholders at the highest marginal combined individual personal income tax rates, manage FSB’s capital level and pay excess capital to its parent holding company, develop management and board of director succession plans for IMB and FSB, and make a decision by June 30, 2017 about whether to raise capital to fund possible debt reduction and share repurchases and to be used for other general corporate purposes. Finally, the IMB Board noted its desire to remain an independent bank holding company, but that it would in furtherance of the exercise of its fiduciary duties to shareholders remain open to considering all possible strategic alternatives.

In early May 2017, the Chief Executive Officer of Party B again contacted IMB through ProBank to express Party B’s continuing interest in effecting a strategic transaction with IMB. At a meeting of IMB’s Board on May 16, 2017, at which IMB’s outside legal counsel and financial adviser participated, the IMB Board discussed an appropriate response to the Party B expression of interest. Following deliberation, at a meeting held on May 18, 2017, the IMB Board instructed ProBank to request subject to terms of confidentiality a term sheet from Party B that would outline in reasonable detail the salient terms of its proposal for further consideration and deliberation of the IMB Board.

Thereafter, on June 7, 2017, Party B communicated a verbal indication of interest through Party B’s independent financial advisor to ProBank. Party B proposed in general terms to acquire IMB for approximately $153 million payable in Party B’s publicly traded common stock, subject to confirmatory due diligence, regulatory approvals and other customary conditions. On June 21, 2017, the IMBFNB Board met with ProBankrepresentatives of Sandler O’Neill and outside legal counsel to IMB to evaluatediscuss the threenon-binding letters of intent. An overall lower valuation and discuss Party B’s indication of interest. The IMB Board also discussed other potential merger partners, the advantages and disadvantageslack of a broad marketing of IMBpublic trading market for sale,Company B’s stock made Company B’s proposal less desirable than the proposals from Company A and IMB’s strategic plan. Glacier was then identifiedGlacier. Based on recent closing stock prices as a result of the discussions as an attractive potential merger partner in viewmeeting date, the value of Company A’s proposal was estimated at $27.32 per FNB share and the value of Glacier’s successful track record with other acquisitions, its emphasisproposal was estimated at $26.84 per FNB share. The FNB Board considered the value of the proposals on locally managed community banking, its strongthat day and over the prior six months. The FNB Board reviewed the attributes of Glacier and Company A stock including valuation multiples, historical stock price performance, daily stock trading volume, quarterly cash dividends and institutional research analyst recommendations. The FNB Board reviewed the historical financial performance and the strong historical performanceacquisition track-record of each of Glacier common stock and related dividend payouts. Following discussion and considerationCompany A, recognizing the deal values for each would fluctuate on a daily basis. The FNB Board considered the strategic implications of the alternatives,Glacier proposal and the IMB Board authorized executive management and ProBankexpectation that based on Glacier’s intention to contact Glacier’s executive management to inquire whether Glacier hadcreate a potential interest in acquiring IMB.

On June 22, 2017, Bruce Gerlach, IMB’s President and Chief Executive Officer, at the directionnew Utah division comprised of the IMB Board, contacted subject to termsoperations of confidentiality representatives at bothFNB’s and Glacier and D. A. Davidson & Co., financial advisor to Glacier (“Davidson”), to see ifBank’s Utah branches, it was expected that a merger with Glacier would have interesta limited impact on FNB’s employees. Additionally, the new division would be able to operate with a certain level of autonomy after the merger, and be better positioned to understand and serve the local community. In contrast, the FNB Board expected that Company A’s proposal would result in discussions aboutmore employee job loss and a potential combinationdisruption to FNB’s business. The FNB Board considered the proposals against FNB’s expected performance on a stand-alone basis. After considering all three proposals and evaluating FNB’s stand-alone prospects, the FNB Board concluded that the Glacier proposal was superior to the other alternatives. Glacier’s long-term stock, dividend performance, stock trading liquidity, community banking model and proposal to continue

FNB’s operations as part of a separate division with IMB. Later that same day, representatives from ProBank sent Davidson information on IMBa local advisory board would best serve its customers, employees and community, and would likely provide a timeline of when they would likehigher value to receive a written indication of interest.

On June 29, 2017, Randy Chesler, Glacier’s Chief Executive Officer, and other representativesshareholders over the long-term, than remaining independent. Accordingly, the FNB Board decided to move forward with the proposal from Glacier, and IMB metsubject to discuss each organization’s approach to community banking and to discusssatisfactory resolution of a possible transaction.

On July 7, 2017, Davidson, on behalf of Glacier, delivered a nonbinding letter of intent setting forth the proposedfew terms of the merger, including the principal financial terms.letter of intent.

On July 14, 2017, the IMB Board met,Between October 28 and October 30, 2018, FNB and Glacier, with the assistance of ProBank and outside legal counsel, to evaluate and discuss Glacier’s nonbinding proposal as well as the status of the discussions with and nonbinding proposal of Party B. As a result of the discussions, the IMB Board determined to invite the chief executive officers of both Glacier and Party B to meet with the IMB Board.

On July 18, 2017, representatives from Glacier and Davidson were invited to present their proposal to the IMB Board in Bozeman, Montana. Following that meeting, ProBank provided to Glacier supplemental information on and answered questions regarding IMB. Representatives of Party B were also invited on July 18, 2017, to present separately their proposal to the IMB Board in Bozeman, Montana. Following the meetings, the IMB Board instructed ProBank to request final indications of interest from both Glacier and Party B to be delivered.

On July 19, 2017, IMB formally engaged ProBank to provide financial advisory services to IMB in respect of the ongoing process.

On July 24, 2017, representatives from IMB, ProBank, Glacier and Davidson participated in a conference call to discuss IMB’syear-to-date financial and operating results, 2017 budget and 2018 and 2019 projections. Between July 7 and July 28, 2017 the parties and theirrespective legal counsel and financial advisors, negotiated several aspects of the term sheet, both financialGlacier’s letter of intent. After several discussions andnon-financial.

On July 26, 2017, Party B delivered an updated consideration, Glacier and FNB signed a nonbinding letter of intent setting forth its updatedon October 30, 2018 which described the principal merger terms of a merger with Party B.

On July 28, 2017, Davidson, on behalf of Glacier, delivered an updated nonbinding letter of intent setting forth the updated terms of the Glacier merger.

On August 2, the IMB Board met with ProBank and legal counsel to discuss the two proposed letters of intent. On the direction of the IMB Board, ProBank presented a counter-proposal to Davidson asking for Glacier to improve its offer in order for IMB to move forwardprovided that FNB would negotiate with Glacier on an exclusive basis. After severalexclusively for a period of 90 days. Accordingly, FNB’s discussions with Company A and review of additional information, Glacier slightly modified and improved its offer and resubmitted its letter of intent on August 2, 2017.

After taking into account both offers, the IMB Board recognized that both were competitive, but determined that Glacier’s long-term stock and dividend performance and its community banking model were in the best interests of its shareholders, and would better serve its customers, employees and the communities in which IMB operates. Accordingly, the IMB Board decided to move forward with the offer from Glacier.

On August 3, 2017 IMB delivered a signed letter of intent to Glacier, executed a formal and mutualnon-disclosure agreement and Glacier provided its due diligence request list to IMB.

On August 7, 2017, Glacier and its advisors were granted access to a virtual data room that containednon-public financial and operational information.

On August 10, 2017, the IMB Board engaged special transactional legal counsel Holland & Hart LLP to represent IMB in connection with the negotiations of a definitive merger agreement consistent with the terms of the Glacier nonbinding letter of intent.

On September 19, 2017, the IMB Board appointed a negotiation committee with authority to negotiate the terms of a definitive merger agreement with Glacier, subject to the final review and, if appropriate, approval of the full IMB Board. Directors Robert Kamp, Bruce Gerlach and Michael Johnson were appointed to the negotiation committee.Company B ceased.

Between August 3October 30, 2018 and October 26, 2017,January 15, 2019, Glacier, IMBFNB and their respective legal counsel and financial advisors conducted appropriate due diligence and drafted and negotiated the merger agreement and related ancillary agreements. Through October 26, 2017, IMBFNB provided Glacier with supplemental information regarding, among other things, the financial aspects of its business, its markets and its operations. Through October 26, 2017, Glacier provided IMBFNB with information regarding, among other things, its employee benefit policies, its insurance policies and itsnon-competition arrangements with its directors and executive officers. Glacier’s due diligence review included a loan due diligence review conducted by DLS Consulting and supported by Glacier’s Chief Credit Officer and a compliance review conducted by Fortner, Bayens, Levkulich & Garrison, P.C. and supported by Glacier’s Audit and Compliance Director.

On August 22September 6 and 23, 2017,7, 2018, representatives from Glacier and Davidson were accompanied by representatives of FNB on a due diligence trip by Bruce Gerlach, Steve Wheeler, FSB’s President, and Mike Johnson, FSB’s Northern Market Manager, to review the branches of FSBFNB and its markets. Mr. Chesler, along with other Glacier representatives and a representative from Davidson, met with representatives from IMB and FSBFNB to discuss the transaction and conduct due diligence interviews.

On September 27, 2017, Davidson madeJanuary 4, 2019, representatives of Glacier informed representatives of FNB that Glacier’s due diligence revealed higher transaction expenses and a presentation to thehigher reserve for loan losses than initially anticipated. As a result, Glacier boardoffered a reduced exchange ratio of directors to discuss the potential transaction, the pro forma financial impact to0.6474 Glacier and the markets that IMB operates in.shares in exchange for each FNB share.

On October 16, 2017,January 9, 2019, representatives from IMB, ProBank,FNB, Sandler O’Neill and Glacier and Davidson participated in a reverse due diligence conference call to provide information to IMBFNB regarding Glacier and answer questions from IMBFNB and ProBank.Sandler O’Neill.

On October 24, 2017,January 10, 2019, the IMBFNB Board, together with ProBankrepresentatives of Sandler O’Neill and legal counsel, met to consider Glacier’s due diligence findings, the reduced exchange ratio and the proposed definitive merger agreement as negotiated to date. Representatives of Sandler O’Neill reviewed the financial aspects of the proposed merger. FNB’s legal counsel reviewed the specific terms of the merger agreement and the substantial process involved in negotiating its terms. The FNB Board considered all these matters and determined that the reduced offer still constituted s significant premium and unanimously confirmed its desire to proceed with the proposed merger.

On January 11, 2019, FNB management conducted onsite diligence at Glacier’s headquarters.

On January 15, 2019, the FNB Board, together with representatives of Sandler O’Neill and legal counsel, again met to consider the negotiated proposed definitive merger agreement. ProBankRepresentatives of Sandler O’Neill reviewed the financial aspects of the proposed merger and rendered to the IMBFNB Board a verbal opinion, which was subsequently confirmed in writing, to the effect that, as of that date and subject to the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by ProBank,Sandler O’Neill, the merger consideration in the proposed merger with Glacier was fair, from a financial point of view, to the holders of IMBFNB common stock. Legal counsel then reviewed the specific terms of the proposed merger agreement and the substantial process involved in negotiating its terms.changes to the proposed merger agreement since the FNB Board’s January 10 meeting. Among other matters considered, the IMBFNB Board reviewed

the specific terms of the merger agreement, the form and value of the consideration to be received by IMBFNB shareholders, the price and historical performance of Glacier common stock and related dividend payouts, current market conditions including comparable bank merger and acquisition transactions, ancillary agreements for the employment of certain FSBFNB employees following the merger, and the implications of the merger to IMB’sFNB’s employees, customers, and communities. After due consideration of these and other matters, and taking into consideration the financial fairness opinion delivered by ProBank,of Sandler O’Neill, the IMBFNB Board unanimously approved entering into the merger agreement.

On October 25, 2017,January 15, 2019, the board of directors of Glacier, together with its legal counsel and representatives of Davidson,Piper Jaffray & Co., met to consider approval of the definitive merger agreement. Davidson presentedPiper Jaffray & Co. provided updated pro forma financial analyses and Glacier’s legal counsel presented a review of the key terms of the merger agreement and related ancillary agreements. Among other matters discussed, the board of directors and Glacier’s advisors discussedsummarized the results of due diligence reviews, the terms of the merger agreement and related ancillary agreements, key pricing metrics, the pro forma financial impact of the merger to Glacier’s shareholders, the benefits of establishing a new bank division in Utah, risks of the merger, and the timing and process for consummation of the merger, including the results of preliminary discussions with bank regulators.merger. After due consideration of these and other matters, the board of directors of Glacier approved the merger agreement on October 25, 2017.agreement.

On October 26, 2017, ProBank delivered to the IMB Board its written opinion to the effect that, as of that date and subject to the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by ProBank, the merger consideration in the proposed merger with Glacier was fair, from a financial point of view, to the holders of IMB common stock, and theThe parties executedentered into the merger agreement and related ancillary agreements.on January 16, 2019. After the close of business on October 26, 2017,January 16, 2019, the parties issued a joint press release announcing the merger.

Reasons For Thefor the Merger – IMBFNB

At a board meeting held on October 24, 2017,January 15, 2019, the IMBFNB Board determined that the terms of the merger agreement were in the best interests of IMBFNB and its shareholders. In the course of reaching this determination and related decision to approve the merger agreement, the IMBFNB Board evaluated the merger and the merger agreement in consultation with the management of IMBFNB and IMB’sFNB’s financial advisor and legal counsel. In reaching its determination, the IMBFNB Board considered a number of factors. Such factors also constituted the reasons that the IMBFNB Board determined to approve the merger agreement and to

recommend that IMBFNB shareholders vote in favor of the merger agreement. Such reasons included the following:

The IMBFNB Board also considered a number of uncertainties and risks in its deliberations concerning the transactions contemplated by the merger agreement, including the following:

The foregoing discussion of the reasons that led the IMBFNB Board to approve the merger agreement and recommend that IMB’sFNB’s shareholders vote in favor of the merger agreement is not intended to be exhaustive but is believed to include all of the material reasons for the IMBFNB Board’s decision. In reaching its determination to approve and recommend the transaction, the IMBFNB Board based its recommendation on the totality of the information presented to it and did not assign any relative or specific weights to the reasons considered in reaching that determination. Individual directors may have given differing weights to different reasons. After deliberating with respect to the merger with Glacier, considering, among other things, the matters discussed above, the IMBFNB Board unanimously approved the merger agreement and the merger with Glacier as being in the best interests of IMBFNB and its shareholders.

Opinion of IMB’sFNB’s Financial Advisor

On July 19, 2017, IMBFNB retained ProBank AustinSandler O’Neill to serveact as exclusivean independent financial advisor to FNB’s board of directors in connection with FNB’s consideration of a possible business combination. Sandler O’Neill is a nationally recognized investment banking firm whose principal business specialty is financial institutions. In the ordinary course of its investment banking business, Sandler O’Neill is regularly engaged in the valuation of financial institutions and their securities in connection with mergers and acquisitions and other corporate transactions.

Sandler O’Neill acted as an independent financial advisor in connection with evaluatingthe proposed transaction and implementing a potential transaction involving the sale or mergerparticipated in certain of the company. ProBank Austin is an investment banking and consulting firm specializing in community bank mergers and acquisitions. IMB selected ProBank Austin as its financial advisor on the basis of its experience and expertise in representing community banks in similar transactions and its familiarity with IMB.

In its capacity as financial advisor, ProBank Austin provided a fairness opinion (the “ProBank Austin Opinion”)negotiations leading to the IMB Board in connection withexecution of the Merger.merger agreement. At the January 15, 2019 meeting at which FNB’s board of directors considered and discussed the terms of the IMB Board on October 24, 2017, ProBank Austin renderedmerger agreement and the merger, Sandler O’Neill delivered to FNB’s board of directors its oral opinion, (whichwhich was subsequently confirmed in writing, by delivery of ProBank Austin’s written opinion dated October 26, 2017) that, based upon and subject to the various factors, assumptions and limitations set forth in such opinion, ProBank Austin representatives’ experience as investment bankers, ProBank Austin’s work as described in such opinion and other factors ProBank Austin deemed relevant,effect that, as of such date,January 15, 2019, the Merger Consideration set forthmerger consideration provided for in the Agreementmerger agreement was fair to the holders of FNB common stock from a financial point of view, to the shareholders of IMB common stock. The ProBank Austin written opinion, dated October 26, 2017, is sometimes referred to herein as the ProBank Austin Opinion.

view.The full text of Sandler O’Neill’s opinion is attached as Appendix C to this proxy statement/prospectus. The opinion outlines the ProBank Austin Opinion, which sets forth, among other things, theprocedures followed, assumptions made, procedures followed, matters considered and qualifications and limitations on the review undertaken by Sandler O’Neill in rendering its opinion, is attached asAppendix C to this proxy statement/prospectus and is incorporated herein by reference.opinion. The summarydescription of the ProBank Austin Opinionopinion set forth hereinbelow is qualified in its entirety by reference to the full text of the opinion. IMBHolders of FNB common shareholders shouldstock are urged to read the full textentire opinion carefully in connection with their consideration of the proposed merger.

Sandler O’Neill’s opinion carefullyspeaks only as of the date of the opinion. The opinion was directed to FNB’s board of directors in connection with its consideration of the merger agreement and in its entirety. The ProBank Austin Opinion is addressedthe merger and does not constitute a recommendation to any shareholder of FNB as to how any such shareholder should vote at any meeting of shareholders called to consider and vote upon the IMB Board, isapproval of the merger agreement and the merger. Sandler O’Neill’s opinion was directed only to the fairness, from a financial point of view, of the Merger Considerationmerger consideration to the holders of IMBFNB common stock and does not constitute a recommendationaddress the underlying business decision of FNB to any shareholder as to how such shareholder should voteengage in the merger, the form or act on any matters relating to the Merger.

The ProBank Austin Opinion was reviewed and approved by the fairness opinion committee of ProBank Austin. ProBank Austin provided its oral opinion to the IMB Board on October 24, 2017 in connection with and for the purposesstructure of the IMB Board’s evaluation of the Merger. ProBank Austin expressed no viewmerger or opinion as to any of the legal, accounting and tax matters relating to the Merger and any other transactions contemplated byin the Agreement or any terms or other aspectsmerger agreement, the relative merits of the Agreementmerger as compared to any other alternative transactions or business strategies that might exist for FNB or the Merger. ProBank Austin expressed no opinion as to the fairness of any consideration paid in connection with the Merger to the holderseffect of any other class of securities, creditors or other constituencies of IMB or as to the underlying decision by IMB to engagetransaction in the Merger or enter into the Agreement. ProBank Austinwhich FNB might engage. Sandler O’Neill did not express any opinion as to the fairness of the amount or nature of the compensation to be received in the Mergermerger by IMB officers, directorsany officer, director or employees,employee of FNB or Glacier Bancorp, Inc. (or, for the purposes of this section, “GBCI”), or any class of such persons, if any, relative to the compensation to be received in the Mergermerger by any other shareholder, including the consideration to be received by the holders of IMBFNB common stock.

The description of the Sandler O’Neill’s opinion set forth below is qualified in its entiretywas approved by reference to the opinion. You should consider the following when reading the discussion of ProBank Austin’sSandler O’Neill’s fairness opinion in this document:

Sandler O’Neill also discussed with certain members of the management of FNB and its representatives the business, financial condition, results of operations and prospects of FNB and held similar discussions with certain members of the management of GBCI and its representatives regarding the business, financial condition, results of operations and prospects of GBCI.

In performing its review, Sandler O’Neill relied upon the accuracy and completeness of all of the financial and other information that was available to and reviewed by Sandler O’Neill from public sources, that was provided to Sandler O’Neill by FNB or GBCI or their respective representatives, or that was otherwise reviewed by Sandler O’Neill, and Sandler O’Neill assumed such accuracy and completeness for purposes of rendering its opinion without any independent verification or investigation. Sandler O’Neill relied on the assurances of the respective managements of FNB and GBCI that they were not aware of any facts or circumstances that would have made any of such information inaccurate or misleading. Sandler O’Neill was not asked to and did not undertake an independent verification of any of such information and Sandler O’Neill did not assume any responsibility or liability for the accuracy or completeness thereof. Sandler O’Neill did not make an independent evaluation or perform an appraisal of the specific assets, the collateral securing assets or the liabilities (contingent or otherwise) of FNB or GBCI or any of their respective subsidiaries, nor was Sandler O’Neill furnished with any such evaluations or appraisals. Sandler O’Neill rendered no opinion or evaluation on the collectability of any assets or the future performance of any loans of FNB or GBCI. Sandler O’Neill did not make an independent evaluation of the adequacy of the allowance for loan losses of FNB or GBCI, or of the combined entity after the merger, and Sandler O’Neill did not review any individual credit files relating to FNB or GBCI. Sandler O’Neill assumed, with the consent of FNB, that the respective allowances for loan losses for both FNB and GBCI were adequate to cover such losses and would be readadequate on a pro forma basis for the combined entity.

In preparing its analyses, Sandler O’Neill used internal net income projections for FNB for the years ending December 31, 2018 through December 31, 2020 with an annual net income growth rate for the years thereafter, as provided by the senior management of FNB, as well as estimated dividends per share for the years ending December 31, 2018 through December 31, 2022, as directed by the senior management of FNB. In addition, Sandler O’Neill used publicly available consensus analyst earnings per share estimates for GBCI for the years ending December 31, 2018 through December 31, 2020, as well as a long-term earnings per share growth rate for the years thereafter and dividend payout ratio for the years ending December 31, 2018 through December 31, 2022, as directed by the senior management of GBCI. Sandler O’Neill also received and used in its entirety;

financial condition, results of operations, business or prospects of FNB or GBCI since the date of the most recent financial statements made available to us. ProBank AustinSandler O’Neill. Sandler O’Neill assumed in all respects material to ourits analysis that IMBFNB and Glacier willGBCI would remain as going concerns for all periods relevant to Sandler O’Neill’s analysis.

Sandler O’Neill also assumed, with FNB’s consent, that (i) each of the analyses,parties to the merger agreement would comply in all material respects with all material terms and conditions of the merger agreement and all related agreements, that all of the representations and warranties contained in the Agreement aresuch agreements were true and correct in all material respects, that each partyof the parties to the Agreement willsuch agreements would perform in all material respects all of the covenants and other obligations required to be performed by such party under the Agreement,such agreements and that the closing conditions precedent in such agreements were not and would not be waived, (ii) in the Agreement are not waived.course of obtaining the necessary regulatory or third party approvals, consents and releases with respect to the merger, no delay, limitation, restriction or condition would be imposed that would have an adverse effect on FNB, GBCI, the merger or any related transactions, and (iii) the merger and any related transactions would be consummated in accordance with the terms of the merger agreement without any waiver, modification or amendment of any material term, condition or agreement thereof and in compliance with all applicable laws and other requirements. Finally, ProBank Austin haswith the consent of FNB, Sandler O’Neill relied upon the advice IMB hasthat FNB received from its legal, accounting and tax advisors as to all legal, accounting and tax matters relating to the Mergermerger and the other transactions contemplated by the Agreement.merger agreement. Sandler O’Neill expressed no opinion as to any such matters.

ProBank Austin has relied, without independent verification, upon the accuracy and completeness of the information it reviewed for the purpose of rendering its opinion. ProBank Austin did not undertake any independent evaluation or appraisal of the assets and liabilities of IMB or Glacier, norSandler O’Neill’s opinion was it furnished with any appraisals. ProBank Austin has not reviewed any individual credit files of IMB or Glacier, and has assumed that IMB’s and Glacier’s allowances are, in the aggregate, adequate to cover inherent credit losses. ProBank Austin’s opinion isnecessarily based on financial, economic, regulatory, market and other conditions existingas in effect on, and the information made available to Sandler O’Neill as of, the date ofthereof. Events occurring after the date thereof could materially affect Sandler O’Neill’s opinion. Sandler O’Neill did not undertake to update, revise, reaffirm or withdraw its opinion. No limitations were imposed by IMB’s boardopinion or its management on ProBank Austin with respectotherwise comment upon events occurring after the date thereof. Sandler O’Neill expressed no opinion as to the investigations madetrading value of GBCI common stock at any time or what the procedures followedvalue of GBCI common stock would be once it is actually received by ProBank Austin in rendering its opinion.the holders of FNB common stock.

In rendering its opinion, ProBank Austin made the following assumptions:

In connection with its opinion, ProBank Austin reviewed:

ProBank Austin also discussed with certain members of senior management of IMB the business, financial condition, results of operations and prospects of IMB, including certain operating, regulatory and other financial matters. We held similar discussions with certain members of senior management of Glacier regarding the business, financial condition, results of operations and prospects of Glacier.

The following is a summary of the material factors considered and analyses performed by ProBank Austin in connection with its opinion dated October 26, 2017.analyses. The summary doesbelow is not purport to be a complete description of the analyses underlying Sandler O’Neill’s opinion or the presentation made by Sandler O’Neill to FNB’s board of directors, but is a summary of all material analyses performed and presented by Sandler O’Neill. The summary includes information presented in tabular format.In order to fully understand the financial analyses, these tables must be read together with the accompanying text. The tables alone do not constitute a complete description of the financial analyses. The preparation of a fairness opinion is a complex process involving subjective judgments as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances. The process, therefore, is not necessarily susceptible to a partial analysis or summary description. Sandler O’Neill believes that its analyses must be considered as a whole and that selecting portions of the factors and analyses to be considered without considering all factors and analyses, or attempting to ascribe relative weights to some or all such factors and analyses, could create an incomplete view of the evaluation process underlying its opinion. Also, no company included in Sandler O’Neill’s comparative analyses described below is identical to FNB or GBCI and no transaction is identical to the merger. Accordingly, an analysis of comparable companies or transactions involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies and other factors that could affect the public trading values or transaction values, as the case may be, of FNB, GBCI and the companies to which they are being compared. In arriving at its opinion, Sandler O’Neill did not attribute any particular weight to any analysis or factor that it considered. Rather, Sandler O’Neill made qualitative judgments as to the significance and relevance of each analysis and factor. Sandler O’Neill did not form an opinion as to whether any individual analysis or factor (positive or negative) considered in isolation supported or failed to support its opinion, rather, Sandler O’Neill made its determination as to the fairness of the merger consideration on the basis of its experience and professional judgment after considering the results of all its analyses taken as a whole.

In performing its analyses, Sandler O’Neill also made numerous assumptions with respect to industry performance, business and economic conditions and various other matters, many of which are beyond the control of FNB, GBCI and Sandler O’Neill. The analyses performed by ProBank Austin. Capitalized terms used herein without definition shall haveSandler O’Neill are not necessarily indicative of actual values or future results, both of which may be significantly more or less favorable than suggested by such analyses. Sandler O’Neill prepared its analyses solely for purposes of rendering its opinion and provided such analyses to FNB’s board of directors at its January 15, 2019 meeting. Estimates on the meanings givenvalues of companies do not purport to such termsbe appraisals or necessarily reflect the prices at which companies or their securities may actually be sold. Such estimates are inherently subject to uncertainty and actual values may be materially different. Accordingly, Sandler O’Neill’s analyses do not necessarily reflect the value of FNB common stock or the prices at which FNB common stock or GBCI common stock may be sold at any time. The analyses of Sandler O’Neill and its opinion were among a number of factors taken into consideration by FNB’s board of directors in making its determination to approve the merger agreement and should not be viewed as determinative of the exchange ratio or the decision of FNB’s board of directors or management with respect to the fairness of the merger. The type and amount of consideration payable in the Agreement.merger were determined through negotiation between FNB and GBCI.

Summary of Financial Terms of Agreement.Exchange Ratio and Implied Transaction Metrics.The Sandler O’Neill reviewed the financial terms of the Agreement provide for Glacierproposed merger. Subject to exchange 4,654,151 shares of its common stock for all ofcertain adjustments and termination provisions, as more fully described in the common stock of IMB. Based on 203,763 shares of IMB common stock outstanding,merger agreement, at the effective time, each share of IMBFNB common stock issued and outstanding prior to the effective time, except for certain shares of FNB common stock as specified in the merger agreement, will be converted into the right to receive 22.8410.6474 shares of GlacierGBCI common stock, subject to certain adjustments.

In addition, IMB shareholders may be entitled to a special dividend immediately prior to the closing of the Merger in an amount equal to the positive difference, if any, between IMB Closing Capital and the Closing Capital Requirement of $73.5 million. IMB Closing Capital will be based on IMB’s shareholders’ equity under generally accepted accounting principles, net of goodwill and other intangible assets, as adjusted by certain items. Factors that will impact IMB Closing Capital include operating

income from July 1, 2017 to the closing, normal tax distribution dividends in accordance with past practice, changes in accumulated other comprehensive income from July 1, 2017 to the closing, and certain Transaction Related Expenses. The amount of the possible special dividend cannot be calculated with a high degree of certainty at this time, and is based in part on factors outside the control of IMB.

The Agreement provides a termination right to IMB under certain circumstances if the Glacier Average Closing Price is less than $28.07 per share unless Glacier agrees to increase the Merger Consideration to $130,642,019 through the issuance of more common shares or payment of cash consideration. Alternatively, the Agreement provides a termination right to Glacier under certain circumstances if the Glacier Average Closing Price is greater than $42.11 per share unless IMB agrees to accept a reduction in Total Stock Consideration through the issuance of fewer shares such that the value of the Merger Consideration is $195,986,299.

stock. Based on 203,763 shares of IMB outstanding common stock, the implied exchange ratio of 22.841 and Glacier’s closing price of $37.26GBCI common stock on October 26, 2017, theJanuary 14, 2019 of $41.66, Sandler O’Neill calculated an implied valuetransaction price per share of the Merger Consideration was $173.4 million in theFNB common stock of $26.97 and an aggregate or $851.06 per share. In addition, IMB shareholders may receive a special cash dividend immediately prior to the closing of the Merger. Based solely on the value of the Per Share Stock Consideration, and giving no credit to any possible special cash dividend, the implied transaction value of $173.4approximately $85.3 million in exchange for all FNB common stock issued and outstanding as of January 14, 2019. Based upon historical financial information for FNB as of or $851.06for the period ended September 30, 2018 and internal earnings per share represents:

IMB Peer Analysis. ProBank Austin compared selected results of First Security Bank’s operating performance to that of 17 selected commercial banks headquartered in Montana, Idaho, Wyoming, North Dakota and South Dakota with total assets between $700 million and $1.5 billion. In addition, the selected peer banks were not part of a larger multi-bank holding company organization (ProBank Austin excluded any bank from the peer analysis that is a subsidiary of a bank holding company with more than $2.5 billion in consolidated assets). ProBank Austin considered this group of financial institutions comparable to First Security Bank on the basis of asset size and geographic location.

This peer group consisted ofFNB, Sandler O’Neill calculated the following banks:implied transaction metrics.

Note:

ProBank AustinFNB Comparable Company Analyses. Sandler O’Neill used publicly available information as of September 30, 2018, unless otherwise noted, the followingand information provided by FNB management as of September 30, 2018, to compare selected financial measuresinformation for the peerFNB with a group as compared to First Security Bank:

YTD =Year-to-Date

PTPP =Pre-TaxPre-Provision = Net Interest Income (FTE) + Noninterest Income - Noninterest Expense

FTE =fully-tax equivalent

Return on Average Assets = ROAA

Return on Average Equity = ROAE

NPAs = Nonperforming assets, defined as loans 90 or more days past due, nonaccrual loans, and Other Real Estate Owned. Restructured loans are not included.

This comparison indicated that First Security Bank was between the 25^th percentile and median of the peer group in termsbanks selected by Sandler O’Neill (the “FNB Peer Group”). The FNB Peer Group consisted of ROAA, ROAE and PTPP earnings to average assets. First Security Bank’s nonperforming asset levels were between the median and the 75^th percentile of the peer group. First Security Bank’s Tier 1 leverage ratio was between the 25^th percentile and median of the peer group, while its total risk-based capital ratio was between the median and 75^th percentile of the peer group.

Comparable Transaction Analysis.ProBank Austin compared the financial performance of certain selling institutions and the prices paid in selected transactions to IMB’s financial performance and the implied transaction multiples being paid by Glacier for IMB. Specifically, ProBank Austin reviewed certain information relating to select bank and thrift transactionspublicly-traded banks headquartered in the nation between November 9, 2016 and October 26, 2017 (with seller’sUnited States with total assets between $750$200 million and $3 billion$500 million and last twelve-monthsyear-to-date return on average equityassets greater than 5.00 percent). Twenty-eight (28) transactions were included in this group based on the selected criterion.1.00%, excluding announced merger targets and companies whose securities trade OTC PINK. The following lists the transactions reviewed by ProBank Austin:

Guideline M&A Transactions

Buyer Name		State		Seller Name		State		Announced Date
Home BancShares Inc.		AR		Stonegate Bank		FL		03/27/17
First Merchants Corp.		IN		Independent Alliance Banks		IN		02/17/17
Heartland Financial USA Inc.		IA		Citywide Banks of Colorado		CO		02/13/17
FB Financial Corp		TN		American City Bk/Clayton Bk		TN		02/08/17
First Busey Corp.		IL		First Community Finl Partners		IL		02/06/17
Bryn Mawr Bank Corp.		PA		Royal Bancshares of PA		PA		01/31/17
Midland States Bancorp Inc.		IL		Centrue Financial Corporation		IL		01/26/17
Simmons First National Corp.		AR		First Texas BHC Inc.		TX		01/23/17
Renasant Corp.		MS		Metropolitan BancGroup Inc.		MS		01/17/17
Columbia Banking System		WA		Pacific Continental Corp.		OR		01/09/17
Veritex Holdings Inc.		TX		Sovereign Bancshares Inc.		TX		12/14/16
Simmons First National Corp.		AR		Southwest Bancorp Inc.		OK		12/14/16
Pacific Premier Bancorp		CA		Heritage Oaks Bancorp		CA		12/13/16
Southern National Bncp of VA		VA		Eastern Virginia Bankshares		VA		12/13/16
CenterState Banks		FL		Gateway Finl Hldgs of FL Inc.		FL		11/30/16
Independent Bk Group Inc.		TX		Carlile Bancshares Inc.		TX		11/21/16

The following table highlights the median results of the guideline M&A transactions:

LTM = Last twelve month

Note: M&A Guideline transactions financial performance based on most recent12-month data.

The median last twelve month ROAA ratio of the selling banks in the guideline transactions was 0.93 percent compared to 0.93 percent for IMB. IMB’s ROAE of 10.23 percent was higher than the peer median of 8.66 percent. The median nonperforming assets (“NPA”) to assets ratio measured 0.70 percent for the guideline transaction group which was higher than 0.48 percent for IMB. The indicated price to tangible book ratio being paid by Glacier for IMB of 231 percent is higher than the median price to tangible book ratio of 196 percent for the guideline transactions. The impliedprice-to-earnings multiple for the IMB transaction with Glacier of 18.9 times was lower than the median multiple of 21.8 times.

IMB Control-Level Valuation.In May 2017, ProBank Austin developed control-level indications of value for IMB based onyear-end 2016 financial information. ProBank Austin developed indications of value using both an income approach and a market approach. ProBank’s indication of value under the income approach measured $149.8 million, while multiple indications of value were developed using the market approach, ranging from $149.6 million to $190.1 million. Based on its analysis, ProBank

advised the IMB Board that a control-level valuation range of between $150 million and $180 million for IMB would be a reasonable expectation in the event the company solicited proposals for an acquisition of the company from one or more third parties.

Glacier Financial Performance and Market Trading Data versus Peer.ProBank Austin compared selected results of Glacier’s operating performance to that of 30 publicly traded banks in the nation with assets between $8.0 billion and $14.0 billion.

This peer group consisted of the following companies:

The analysis compared financial information as of September 30, 2018 for FNB, as provided by FNB senior management, with the corresponding publicly available data for the FNB Peer Group as of September 30, 2018 (unless otherwise noted) with pricing data as of January 14, 2019. The table below sets forth the data for FNB and the high, low, mean and median data for the FNB Peer Group.

Note:

FNB Net Present Value Analyses. Sandler O’Neill performed an analysis that estimated the net present value per share of FNB common stock assuming FNB performed in accordance with internal net income projections for FNB for the years ending December 31, 2018 through December 31, 2020 with an annual net income growth rate for the years ending December 31 2021 through December 31, 2022, as provided by the senior management of FNB, as well as estimated dividends per share for the years ending December 31, 2019 through December 31, 2022, as directed by the senior management of FNB. To approximate the terminal value of a share of FNB common stock at December 31, 2022, Sandler O’Neill applied price to 2022 earnings per share multiples ranging from 10.00x to 16.67x and price to December 31, 2022 tangible book value per share multiples ranging from 110% to 185%. The terminal values were then discounted to present values using different discount rates ranging from 9.0% to 15.0% which were chosen to reflect different assumptions regarding required rates of return of holders or prospective buyers of FNB common stock. As illustrated in the following tables, the analysis indicated an imputed range of values per share of FNB common stock of $15.68 to $30.29 when applying multiples of earnings per share and $13.33 to $25.65 when applying multiples of tangible book value per share.