2020 census
As of the 2020 census, there were 11,059 people, 4,576 households, and 2,804 families residing in the county. [14] Of the residents, 22.0% were under the age of 18 and 19.7% were 65 years of age or older; the median age was 40.0 years. For every 100 females there were 109.5 males, and for every 100 females age 18 and over there were 108.8 males. [14]
The population density was 19.6 inhabitants per square mile (7.6/km2). There were 5,658 housing units, of which 19.1% were vacant. Among occupied housing units, 71.2% were owner-occupied and 28.8% were renter-occupied. The homeowner vacancy rate was 1.8% and the rental vacancy rate was 12.5%. [14]
The racial makeup of the county was 91.7% White, 1.0% Black or African American, 1.2% American Indian and Alaska Native, 0.6% Asian, 1.6% from some other race, and 3.8% from two or more races. Hispanic or Latino residents of any race comprised 5.5% of the population. [15]
Of the 4,576 households, 25.1% had children under the age of 18 living with them and 20.4% had a female householder with no spouse or partner present. About 32.2% of all households were made up of individuals and 13.8% had someone living alone who was 65 years of age or older. [14]
2010 census
As of the 2010 census, there were 11,200 people, 4,483 households, and 2,814 families in the county. The population density was 19.9 inhabitants per square mile (7.7/km2). There were 5,559 housing units at an average density of 9.9 units per square mile (3.8 units/km2). The racial makeup of the county was 96.2% white, 0.7% Asian, 0.7% American Indian, 0.5% black or African American, 0.8% from other races, and 1.1% from two or more races. Those of Hispanic or Latino origin made up 1.6% of the population. In terms of ancestry, 50.7% were German, 20.6% were Norwegian, 12.4% were Irish, 6.6% were English, 6.2% were Dutch, 5.0% were Danish, and 5.0% were American.
Of the 4,483 households, 26.7% had children under the age of 18 living with them, 53.0% were married couples living together, 6.8% had a female householder with no husband present, 37.2% were non-families, and 30.9% of all households were made up of individuals. The average household size was 2.30 and the average family size was 2.88. The median age was 39.9 years.
The median income for a household in the county was $45,606 and the median income for a family was $57,753. Males had a median income of $36,370 versus $25,898 for females. The per capita income for the county was $22,447. About 6.5% of families and 12.1% of the population were below the poverty line, including 12.8% of those under age 18 and 8.8% of those age 65 or over.
United States
South Dakota 
