Exhibit 99.1

FIRST INTERSTATE BANCSYSTEM, INC. Proxy for annual meeting of shareholders on may 24, 2017 solicited on Behalf of the Board of directors The undersigned hereby appoints James R. Scott and Kevin P. Riley, and each of them, with full power of substitution and power to act alone, as proxies to vote all the shares of common stock that the undersigned would be entitled to vote if personally present and acting at the Annual Meeting of Shareholders of First Interstate BancSystem, Inc., to be held on Wednesday, May 24, 2017, at 4:00 p.m., Mountain Daylight Time, at the First Interstate Bank Operations Center, 1800 Sixth Avenue North, Billings, Montana 59101, and at any adjournments or postponements thereof, as follows: (continued and to be signed on the reverse side.)

aNNual mEETiNG Of shaREhOldERs Of fiRsT iNTERsTaTE BaNcsysTEm, iNc. may 24, 2017 PROXy vOTiNG iNsTRucTiONs iNTERNET - Access “www.voteproxy.com” and follow the on-screen instructions or scan the QR code with your smartphone. Have your proxy card available when you access the web page. TELEPhONE - Call toll-free 1-800-PROXiEs (1-800-776-9437) in the United States or 1-718-921-8500 from foreign countries from any touch-tone telephone and follow the instructions. Have your proxy card available when you call. Vote online/phone until 11:59 PM EST the day before the meeting. mail - Sign, date and mail your proxy card in the envelope provided as soon as possible. iN PERsON - You may vote your shares in person by attending the Annual Meeting. GO GREEN - e-Consent makes it easy to go paperless. With e-Consent, you can quickly access your proxy material, statements and other eligible documents online, while reducing costs, clutter and paper waste. Enroll today via www.astfinancial.com to enjoy online access. cOmPaNy NumBER accOuNT NumBER NOTicE Of iNTERNET availaBiliTy Of PROXy maTERial: The Notice of Meeting, proxy statement/prospectus and proxy card are available at http://www.astproxyportal.com/ast/40019/ Please detach along perforated line and mail in the envelope provided IF you are not voting via telephone or the Internet. 00033300333333433000 5 052417 ThE BOaRd Of diREcTORs REcOmmENds yOu vOTE “fOR” Each Of ThE PROPOsals, “fOR” Each Of ThE diREcTOR NOmiNEEs aNd fOR ThE OPTiON Of “TwO yEaRs” ON PROPOsal 6. PlEasE siGN, daTE aNd RETuRN PROmPTly iN ThE ENclOsEd ENvElOPE. PlEasE maRK yOuR vOTE iN BluE OR BlacK iNK as shOwN hERE This proxy, when properly executed, will be voted in the manner directed herein. If no such direction is made, this proxy will be voted in accordance with the Board of Directors’ recommendations. To indicate changes change your to the the new address registered address on name(s) your in the account, address on the please account space check above may not the . Please be box submitted at note right and that via this method. 1. Vote on the merger agreement, dated November 17, 2016, by and between First FOR AGAINST ABSTAIN Interstate BancSystem, Inc. and Cascade Bancorp pursuant to which Cascade will merge with and into First Interstate. 2. Vote on the amended and restated articles of incorporation of First Interstate BancSystem, Inc. 3. Vote on a proposal to adjourn the special meeting to a later date or dates, if necessary, to permit further solicitation of proxies if there are insufficient votes at the time of the special meeting to approve the merger agreement. 4. Election of Directors Nominees (1) Steven J. Corning (2) Dana L. Crandall (3) Charles E. Hart. M.D. (4) Charles M. Heyneman (5) Peter I. Wold 5. Vote on a non-binding advisory resolution on executive compensation 1 year 2 years 3 years ABSTAIN 6. Vote on frequency of non-binding advisory resolution on executive compensation FOR AGAINST ABSTAIN 7. Ratification of RSM US, LLP as our independent registered public accounting firm for 2017 8. Vote on the amended and restated bylaws of First Interstate BancSystem, Inc. NOTE: Such other business as may properly come before the meeting or any adjournment thereof. Signature of Shareholder Date: Signature of Shareholder Date: Note: Please title as such. sign exactly If the signer as your is a name corporation, or names please appear sign on full this corporate Proxy. When name shares by duly are authorized held jointly, officer, each giving holder full should title as sign. such. When If signer signing is a as partnership, executor, please administrator, sign in attorney, partnership trustee name or by guardian, authorized please person. give full