Adjacent counties

Major highways

National protected areas

2020 census

As of the 2020 census, there were 9,371 people living in the county.^{[citation needed]}

2010 census

As of the 2010 census, there were 9,246 people, 4,014 households, and 2,383 families living in the county. The population density was 1.7 inhabitants per square mile (0.66/km²). There were 5,273 housing units at an average density of 1.0 per square mile (0.39/km²). The racial makeup of the county was 94.8% white, 1.4% American Indian, 0.4% Pacific islander, 0.4% Asian, 0.2% black or African American, 1.2% from other races, and 1.6% from two or more races. Those of Hispanic or Latino origin made up 3.7% of the population. In terms of ancestry, 26.5% were German, 23.9% were English, 15.4% were Irish, 7.9% were Norwegian, 6.5% were Scottish, and 3.4% were American.

Of the 4,014 households, 23.8% had children under the age of 18 living with them, 49.9% were married couples living together, 6.4% had a female householder with no husband present, 40.6% were non-families, and 33.0% of all households were made up of individuals. The average household size was 2.19 and the average family size was 2.79. The median age was 42.0 years.

The median income for a household in the county was $38,264 and the median income for a family was $53,036. Males had a median income of $35,568 versus $27,314 for females. The per capita income for the county was $21,110. About 10.8% of families and 15.0% of the population were below the poverty line, including 14.4% of those under age 18 and 6.0% of those age 65 or over.

City

• Dillon (county seat)

Town

• Lima

Census-designated places

Other unincorporated communities

Former communities

• Armstead - flooded by Clark County Reservoir in 1964
• Bannack (presently a National Historic Monument and site of Bannack State Park)
• Hecla
• Lion City