Adjacent counties

National protected area

• Lewis and Clark National Forest (part)
• Rocky Mountain Front Conservation Area (part)

2020 census

As of the 2020 census, there were 6,226 people living in the county.^{[citation needed]}

2010 census

As of the 2010 census, there were 6,073 people, 2,450 households, and 1,643 families residing in the county. The population density was 2.7 inhabitants per square mile (1.0/km²). There were 2,892 housing units at an average density of 1.3 units per square mile (0.50 units/km²). The racial makeup of the county was 96.3% white, 1.4% American Indian, 0.1% Asian, 0.2% from other races, and 1.9% from two or more races. Those of Hispanic or Latino origin made up 1.3% of the population. In terms of ancestry, 40.2% were German, 14.7% were Norwegian, 14.5% were Irish, 11.9% were English, 6.4% were Swedish, 6.0% were Dutch, and 4.3% were American.

Of the 2,450 households, 25.7% had children under the age of 18 living with them, 58.2% were married couples living together, 6.0% had a female householder with no husband present, 32.9% were non-families, and 29.3% of all households were made up of individuals. The average household size was 2.29 and the average family size was 2.83. The median age was 45.8 years.

The median income for a household in the county was $39,516 and the median income for a family was $49,102. Males had a median income of $34,824 versus $24,419 for females. The per capita income for the county was $20,509. About 11.0% of families and 12.8% of the population were below the poverty line, including 13.3% of those under age 18 and 13.5% of those age 65 or over.

City

• Choteau (county seat)

Towns

• Dutton
• Fairfield

Census-designated places

• Bynum
• Miller Colony
• New Rockport Colony
• Pendroy
• Power
• Rockport Colony

Unincorporated communities

• Agawam