Chouteau County, MT adjoins Cascade County at I-15's western border with an area covering 2172 square miles across northcentral Montana's Hi-Line region; it had an estimated population of 6154 people by 2018 estimates—making Chouteau one of Montana's least populous counties yet still having small cities like Fort Benton (county seat) populated with thousands each year during tourist season due to its historic attractions like old jailhouse museum & riverboat port tours around Upper Missouri River access points through town while more rural areas make up majority land acreage & their focus remains on agriculture/ranching activities like wheat farming & raising livestock livestock raising).