Major highways

Adjacent counties

National protected areas

• Black Hills National Forest (part)
• Devils Tower National Monument
• Thunder Basin National Grassland (part)

2000 census

As of the 2000 United States Census,^[9] of 2000, there were 5,887 people, 2,308 households, and 1,645 families in the county. The population density was 2 people per square mile (0.77 people/km²). There were 2,935 housing units at an average density of 1.0 units per square mile (0.39 units/km²). The racial makeup of the county was 97.86% White, 0.05% Black or African American, 1.02% Native American, 0.07% Asian, 0.25% from other races, and 0.75% from two or more races. 0.92% of the population were Hispanic or Latino of any race. 34.1% were of German, 14.6% English, 7.8% Irish and 6.8% American ancestry.

There were 2,308 households, out of which 32.30% had children under the age of 18 living with them, 62.30% were married couples living together, 5.40% had a female householder with no husband present, and 28.70% were non-families. 24.90% of all households were made up of individuals, and 10.30% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.01.

The county population contained 26.90% under the age of 18, 6.60% from 18 to 24, 24.60% from 25 to 44, 27.20% from 45 to 64, and 14.70% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 102.40 males. For every 100 females age 18 and over, there were 101.80 males.

The median income for a household in the county was $35,601, and the median income for a family was $43,105. Males had a median income of $34,483 versus $18,967 for females, indicating a relatively high level of income inequality based on gender. The per capita income for the county was $17,379. About 7.8% of families and 9.10% of the population were below the poverty line, including 9.90% of those under age 18 and 11.80% of those age 65 or over.

2010 census

As of the 2010 United States Census, there were 7,083 people, 2,921 households, and 2,016 families in the county.^[10] The population density was 2.5 people per square mile (0.97 people/km²). There were 3,595 housing units at an average density of 1.3 units per square mile (0.50 units/km²).^[11] The racial makeup of the county was 97.2% white, 0.7% American Indian, 0.2% black or African American, 0.2% Asian, 0.6% from other races, and 1.2% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population.^[10] In terms of ancestry, 38.8% were German, 16.5% were English, 14.5% were Irish, 9.5% were Swedish, and 3.8% were American.^[12]

Of the 2,921 households, 28.4% had children under the age of 18 living with them, 59.2% were married couples living together, 6.5% had a female householder with no husband present, 31.0% were non-families, and 25.0% of all households were made up of individuals. The average household size was 2.41 and the average family size was 2.90. The median age was 43.6 years.^[10]

The median income for a household in the county was $49,890 and the median income for a family was $55,765. Males had a median income of $47,821 versus $32,217 for females. The per capita income for the county was $24,520. About 6.5% of families and 7.8% of the population were below the poverty line, including 10.8% of those under age 18 and 8.0% of those age 65 or over.^[13]

Towns

Census-designated place

• Beulah

Unincorporated communities