2020 census
As of the 2020 census, there were 6,336 people, 2,474 households, and 1,685 families residing in the county. [12] The population density was 12.2 inhabitants per square mile (4.7/km2). [12]
Of the residents, 26.9% were under the age of 18 and 19.7% were 65 years of age or older; the median age was 41.0 years. For every 100 females there were 103.1 males, and for every 100 females age 18 and over there were 102.8 males. [12]
The racial makeup of the county was 76.5% White, 0.3% Black or African American, 12.0% American Indian and Alaska Native, 1.4% Asian, 3.2% from some other race, and 6.5% from two or more races. Hispanic or Latino residents of any race comprised 5.0% of the population. [13]
There were 2,474 households in the county, of which 31.5% had children under the age of 18 living with them and 21.3% had a female householder with no spouse or partner present. About 26.9% of all households were made up of individuals and 13.0% had someone living alone who was 65 years of age or older. [12]
There were 2,728 housing units, of which 9.3% were vacant. Among occupied housing units, 76.3% were owner-occupied and 23.7% were renter-occupied. The homeowner vacancy rate was 1.3% and the rental vacancy rate was 12.3%. [12]
2010 census
As of the 2010 census, there were 6,486 people, 2,554 households, and 1,751 families in the county. The population density was 12.5 inhabitants per square mile (4.8/km2). There were 2,824 housing units at an average density of 5.4 units per square mile (2.1 units/km2). The racial makeup of the county was 81.0% white, 14.0% American Indian, 1.1% Asian, 0.5% black or African American, 0.7% from other races, and 2.7% from two or more races. Those of Hispanic or Latino origin made up 1.7% of the population. In terms of ancestry, 39.9% were German, 20.1% were Norwegian, 8.9% were Irish, 6.1% were Dutch, 5.1% were English, and 1.6% were American.
Of the 2,554 households, 30.9% had children under the age of 18 living with them, 54.3% were married couples living together, 8.8% had a female householder with no husband present, 31.4% were non-families, and 27.4% of all households were made up of individuals. The average household size was 2.48 and the average family size was 3.00. The median age was 40.5 years.
The median income for a household in the county was $52,354 and the median income for a family was $61,667. Males had a median income of $36,364 versus $30,854 for females. The per capita income for the county was $24,948. About 4.7% of families and 7.1% of the population were below the poverty line, including 8.8% of those under age 18 and 13.1% of those age 65 or over.
United States
South Dakota 
