<ACCESSION-NUMBER>0000860413-19-000117 <TYPE>10-Q <PUBLIC-DOCUMENT-COUNT>90 <PERIOD>20190630 <FILING-DATE>20190807 <DATE-OF-FILING-DATE-CHANGE>20190807 <FILER> <COMPANY-DATA> <CONFORMED-NAME>FIRST INTERSTATE BANCSYSTEM INC <CIK>0000860413 <ASSIGNED-SIC>6022 <IRS-NUMBER>810331430 <STATE-OF-INCORPORATION>MT <FISCAL-YEAR-END>1231 </COMPANY-DATA> <FILING-VALUES> <FORM-TYPE>10-Q <ACT>34 <FILE-NUMBER>001-34653 <FILM-NUMBER>191005414 </FILING-VALUES> <BUSINESS-ADDRESS> <STREET1>P O BOX 30918 <STREET2>401 NO 31ST STREET <CITY>BILLINGS <STATE>MT <ZIP>59116-0918 <PHONE>4062555300 </BUSINESS-ADDRESS> <MAIL-ADDRESS> <STREET1>P O BOX 30918 <STREET2>401 NO 31ST STREET <CITY>BILLINGS <STATE>MT <ZIP>59116-0918 </MAIL-ADDRESS> <FORMER-COMPANY> <FORMER-CONFORMED-NAME>FIRST INTERSTATE BANCSYSTEM OF MONTANA INC <DATE-CHANGED>19930615 </FORMER-COMPANY> </FILER>