Exhibit 99.11

Voting Agreement and Irrevocable Proxy

(Gunther Shareholders)

This Voting Agreement and Irrevocable Proxy, dated as of May 17, 2021 (this “Agreement”), is made by and among Glacier Bancorp, Inc. (“GBCI”), Glacier Bank, a wholly owned subsidiary of GBCI (“Glacier Bank”), Altabancorp (“AB”), Altabank, a wholly owned subsidiary of AB (“Altabank”), and the undersigned, each of whom is a shareholder of AB (each, a “Shareholder”). This Agreement is effective upon the signing of the Merger Agreement (as defined below).

Recital

As an inducement for GBCI, Glacier Bank, AB, and Altabank to enter into the Plan and Agreement of Merger, dated May 17, 2021 (the “Merger Agreement”), under which, among other things, AB will merge with and into GBCI (the “Merger”), and Altabank will merge with and into Glacier Bank, each Shareholder agrees as follows:

Agreement

Voting of Shares. Each Shareholder irrevocably and unconditionally agrees to vote or cause to be voted (including by proxy or written consent, if applicable) at any shareholder meeting of AB, or any adjournment or postponement thereof, including any meeting called for the purpose of approving the Merger Agreement (an “AB Meeting”), all shares of AB common stock that such Shareholder owns of record or beneficially, or acquires after the date hereof but prior to the record date, in either case with power to vote or direct the voting of such shares (collectively, the “Owned Shares”), (a) in favor of (i) approval of the Merger Agreement and the transactions contemplated therein, including the Merger, and (ii) any proposal to adjourn or postpone such meeting to a later date if there are not sufficient votes to approve the Merger Agreement, and (b) against any action, proposal, transaction, or agreement that would reasonably be likely to (i) result in a breach of any covenant, representation, or warranty or any other obligation or agreement of AB contained in the Merger Agreement, or of the Shareholder contained in this Agreement, or (ii) materially prevent, impede, interfere with, delay, or frustrate the purposes of or materially and adversely affect the completion of the transactions contemplated by the Merger Agreement, including the Merger; provided, however, that each Shareholder’s voting obligations under this Section 1 will not apply with respect to any vote on the Merger Agreement if the Merger Agreement is amended so as to reduce the amount or change the form of consideration to be received by the shareholders of AB, impose any material condition to the receipt of the consideration to be received by the shareholders of AB, or change the tax consequences of the receipt thereof under the Merger Agreement in its present form (an “Adverse Change”). For the avoidance of doubt, the foregoing commitments apply to any Owned Shares held by any trust, limited partnership, limited liability company, corporation, or other entity holding shares of AB common stock for which the Shareholder serves in any trustee, partner, member, shareholder, or similar capacity. To the extent the Shareholder does not control (by himself, herself, or itself) the determinations of such shareholder entity, the Shareholder agrees to exercise all voting or other determination rights the Shareholder has in such shareholder entity to carry out the intent and purposes of the Shareholder’s voting obligations under this Section 1 and as otherwise set forth in this Agreement.

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No Solicitation. Solely in his, her, or its capacity as a record or beneficial owner of the Owned Shares, each Shareholder hereby agrees that during the term of this Agreement, the Shareholder shall not knowingly, and shall direct his, her, or its advisors and representatives not to, directly or indirectly, (a) take any of the actions specified in Section 4.1.9 of the Merger Agreement, or (b) participate in, directly or indirectly, a solicitation of proxies or powers of attorney or similar rights to vote, or seek to advise or influence any person with respect to the voting of, any shares of AB common stock in connection with any vote or other action on any matter of a type described in Section 1 of this Agreement, other than to recommend that shareholders of AB vote in favor of the adoption and approval of the Merger Agreement, the Merger and the transactions contemplated by the Merger Agreement, and as otherwise expressly permitted by this Agreement. Each Shareholder agrees, solely in his, her, or its capacity as a record or beneficial owner of the Owned Shares, immediately to cease and cause to be terminated any activities, discussions, or negotiations conducted before the date of this Agreement with any persons other than GBCI and Glacier Bank with respect to any possible Acquisition Proposal (as defined in the Merger Agreement) and will take all necessary steps to inform any investment banker, financial advisor, attorney, accountant, or other representative retained by the Shareholder of the obligations undertaken by the Shareholder pursuant to this Section 2.

Ownership. On the date of this Agreement, each Shareholder represents and warrants, severally but not jointly, that the Owned Shares set forth on such Shareholder’s signature page (a) are owned of record or beneficially by the Shareholder in the manner reflected on the Shareholder’s signature page, (b) include all of the shares of AB common stock owned of record or beneficially by the Shareholder as of the date of this Agreement, and (c) are free and clear of any proxy or voting restriction, claims, liens, encumbrances, and security interests, except (if applicable) as set forth on the Shareholder’s signature page, which encumbrances or other items do not affect the ability of the Shareholder to perform his, her, or its obligations under this Agreement. As of the date of this Agreement, each Shareholder has, and at any AB Meeting each Shareholder will have (except as otherwise permitted by this Agreement), sole voting power and sole dispositive power with respect to all of the Shareholder’s Owned Shares, except as otherwise reflected on the Shareholder’s signature page.

Proxy.

Appointment of Proxy. In order to better effect the provisions set forth in Section 1, each Shareholder revokes any previously executed proxies and constitutes and appoints Adelaide Maudsley with full power of substitution, such Shareholder’s true and lawful proxy and attorney-in-fact (the “Proxy Holder”) to vote at any AB Meeting all of such Shareholder’s Owned Shares as provided in Section 1, with such modifications to the Merger Agreement as the parties to the Merger Agreement may make; provided, however, that this proxy will not apply with respect to any vote on the Merger Agreement if an Adverse Change occurs. This irrevocable proxy shall automatically terminate upon termination of this Agreement.

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Substitute Proxy. If for any reason the Proxy Holder becomes unable to perform his duties as Proxy Holder under this Agreement, each Shareholder appoints Mark K. Olson or his designee (the “Substitute”) as substitute proxy to act as the Proxy Holder and vote all of such Shareholder’s Owned Shares at any AB Meeting as provided in Section 1, with such modifications to the Merger Agreement as the parties to the Merger Agreement may make; provided, however, that this proxy will not apply with respect to any vote on the Merger Agreement if an Adverse Change occurs. Notwithstanding the above, the Proxy Holder may from time to time, in his discretion, appoint any other substitute proxy to act as the Proxy Holder upon prior written notice to GBCI and AB.

Acknowledgments. Each Shareholder acknowledges that GBCI and AB are relying on this Agreement in incurring expenses in connection with the transactions contemplated by the Merger Agreement and that the proxy granted under this Agreement is coupled with an interest and is irrevocable to the fullest extent permitted by applicable law. The vote of the Proxy Holder (and upon substitution, the Substitute under Section 4.b.) will control in any conflict between such vote of the Owned Shares and a vote by any substitute proxy holder or the Shareholder, and AB agrees to recognize the vote of the Proxy Holder or upon substitution, the Substitute.

No Transfer. Until the termination of this Agreement pursuant to Section 7.i, no Shareholder will sell, transfer, permit a lien or other encumbrance to be created with respect to, or grant any proxy in respect of (except for proxies solicited by the board of directors of AB in connection with the AB Meeting at which the Merger Agreement is presented for shareholder approval) any of the Owned Shares, unless all other parties to any such sale or other transaction enter into an agreement in form and substance satisfactory to GBCI embodying the benefits and rights contained in this Agreement.

Miscellaneous.

Individual Obligations. The obligations of each of the signatories to this Agreement are independent of one another and are not intended to be joint obligations of the undersigned. This Agreement is intended to be enforceable by GBCI or Glacier Bank against each Shareholder individually.

Binding Effect. This Agreement will inure to the benefit of, and will be binding upon, each Shareholder’s heirs or legal representatives.

Severability. If any provision of this Agreement or the application of such provision to any person or circumstances will be held invalid or unenforceable by a court of competent jurisdiction, such provision or application will be unenforceable only to the extent of such invalidity or unenforceability, and the remainder of the provision held invalid or unenforceable and the application of such provision to persons or circumstances, other than the party as to which it is held invalid, and the remainder of this Agreement, will not be affected.

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Reformation. If any court determines that the obligations and restrictions set forth in this Agreement are unenforceable, then the parties request such court to reform any unenforceable provisions to the maximum obligations or restrictions, term, and scope, as applicable, that such court finds enforceable.

Expenses. Except as otherwise may be agreed in writing, all costs, fees, and expenses incurred in connection with this Agreement and the transactions contemplated hereby shall be paid by the party incurring such costs, fees, and expenses. Notwithstanding the preceding sentence or anything else to the contrary in this Agreement, following the earlier to occur of (a) an AB Meeting (so long as the Shareholders have complied with their obligations in paragraph 1) or (b) the termination of the Merger Agreement prior to an AB Meeting other than as a result of a violation of this Agreement by a Shareholder, AB shall promptly reimburse the reasonable and documented legal, advisory and related fees and expenses of the Shareholders (and each of them) incurred in connection with their entry into and compliance with the Shareholder Agreement, including without limitation their related compliance with the laws and regulations applicable thereto, their communications (public and otherwise) with and among GCBI and AB and their respective advisors, with and among the other shareholders of AB, and any and other acts (including omissions to act) relating directly or indirectly to their ownership of equity securities of AB since January 1, 2020; provided, that AB will not be required to reimburse the Shareholders for more than $550,000 in the aggregate. For the avoidance of doubt, (i) documentation of fees and expenses shall be acceptable if AB is provided with evidence of payment or with an appropriately redacted invoice reflecting the basis of such fees and expenses, and (ii) reimbursable costs and expenses shall not include brokerage commissions or asset-based investment advisory fees incurred as a result of the purchase, ownership or sale of AB securities.

Amendments; Waivers. Any provision of this Agreement may be amended or waived if, and only if, such amendment or waiver is in writing and signed (i) in the case of an amendment, by GBCI and the Shareholder to be bound by such amendment and (ii) in the case of a waiver, by the party against whom the waiver is to be effective. No failure or delay by any party in exercising any right, power, or privilege under this Agreement shall operate as a waiver thereof, nor shall any single or partial exercise thereof preclude any other or further exercise thereof or the exercise of any other right, power, or privilege.

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Governing Law; Venue. This Agreement will be governed by and construed in accordance with the laws of the State of Montana, except to the extent that federal law may govern certain matters. The parties must bring any legal proceeding arising out of this Agreement in the state courts situated in Kalispell, Montana or the federal district courts of the Missoula Division for the State of Montana. Each party consents to and submits to the jurisdiction of any such court.

Remedies. Any breach of this Agreement entitles GBCI to injunctive relief and/or specific performance, as well as to any other legal or equitable remedies it may be entitled to, it being agreed that money damages alone would be an inadequate remedy for such breach. The rights and remedies of the parties to this Agreement are cumulative and not alternative.

Termination of Agreement. This Agreement shall be effective from the date of this Agreement and shall terminate and be of no further force and effect upon the earlier to occur of (i) the Effective Time (as defined in the Merger Agreement), (ii) such date and time as termination of the Merger Agreement in accordance with its terms, (iii) upon mutual written agreement of the parties hereto to terminate this Agreement, (iv) an Adverse Change or (v) the date the Owned Shares have been voted in favor of approval of the Merger Agreement and the transactions contemplated therein, including the Merger, at the AB Meeting, provided that at least a majority of the outstanding shares of AB common stock entitled to vote have been voted in favor of approval of the Merger Agreement and the transactions contemplated therein, including the Merger, at the AB Meeting. Upon termination of this Agreement, no party shall have any further obligations or liabilities under this Agreement.

Shareholder Agreement. Each Shareholder that is a party to that certain Shareholder Agreement, dated January 28, 2020 (the “Shareholder Agreement”), waives any terms set forth in the Shareholder Agreement that may limit or otherwise restrict such Shareholder’s obligations under this Agreement (e.g., under Section 6(a) of the Shareholder Agreement or otherwise). In the event the terms of the Shareholder Agreement conflict with the terms of this Agreement, the terms of this Agreement will control.

Counterparts. This Agreement may be executed in one or more counterparts, including facsimile and/or scanned counterparts, each of which will be deemed an original, but all of which taken together will constitute one and the same document. The parties agree that facsimile or electronic signatures shall have the same force and effect as original signatures.

[Signatures appear on the following pages]

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Altabancorp SC 13D/A