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                            November 9, 2021

       Kevin P. Riley
       President and Chief Executive Officer
       First Interstate BancSystem, Inc.
       401 North 31st Street
       Billings, MT 59101

                                                        Re: First Interstate
BancSystem, Inc.
                                                            Registration
Statement on Form S-4
                                                            Filed November 4,
2021
                                                            File No. 333-260771

       Dear Mr. Riley:

              This is to advise you that we have not reviewed and will not
review your registration
       statement.

               Please refer to Rules 460 and 461 regarding requests for
acceleration. We remind you
       that the company and its management are responsible for the accuracy and
adequacy of their
       disclosures, notwithstanding any review, comments, action or absence of
action by the staff.

                                                        Please contact Eric
Envall at (202) 551-3234 with any questions.




                            Sincerely,


                            Division of Corporation Finance

                            Office of Finance