UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D.C. 20549 FORM 10-K (Mark One) ☑ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2020 or ☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from to . Commission File Number: 001-34653 FIRST INTERSTATE BANCSYSTEM, INC. (Exact name of registrant as specified in its charter) Montana 81-0331430 | --- | --- | --- ...