The terrain of Day County consists of rolling hills, partly devoted to agriculture. It is dotted with numerous lakes and ponds, especially its eastern portion.[5] The terrain slopes to the west; its highest point is the northeast corner, at 2,014 ft (614 m) ASL.[6]
The county has a total area of 1,091 square miles (2,830 km2), of which 1,028 square miles (2,660 km2) is land and 63 square miles (160 km2) (5.8%) is water.[7]
U.S. Decennial Census[16] 1790-1960[17] 1900-1990[18] 1990-2000[19] 2010-2020[1]
2020 census
As of the 2020 census, there were 5,449 people, 2,370 households, and 1,451 families residing in the county.[20] The population density was 5.3 inhabitants per square mile (2.0/km2). There were 3,395 housing units.
The median income for a household in the county was $57,558 and the median income for a family was $76,583. About 13.1% of families and 14.7% of the population were below the poverty line, including 21.5% of those under age 18 and 11.9% of those age 65 or over.
2010 census
As of the 2010 census, there were 5,710 people, 2,504 households, and 1,561 families in the county. The population density was 5.6 inhabitants per square mile (2.2/km2). There were 3,630 housing units at an average density of 3.5 units per square mile (1.4 units/km2). The racial makeup of the county was 88.1% white, 9.5% American Indian, 0.2% Asian, 0.1% black or African American, 0.4% from other races, and 1.7% from two or more races. Those of Hispanic or Latino origin made up 1.1% of the population. In terms of ancestry, 43.8% were German, 25.1% were Norwegian, 12.8% were Polish, 8.8% were Irish, and 6.1% were American.
Of the 2,504 households, 24.4% had children under the age of 18 living with them, 50.0% were married couples living together, 7.9% had a female householder with no husband present, 37.7% were non-families, and 34.0% of all households were made up of individuals. The average household size was 2.22 and the average family size was 2.83. The median age was 47.9 years.
The median income for a household in the county was $36,818 and the median income for a family was $47,949. Males had a median income of $36,549 versus $25,750 for females. The per capita income for the county was $20,542. About 10.7% of families and 12.5% of the population were below the poverty line, including 11.7% of those under age 18 and 14.1% of those age 65 or over.
Day County voters have tended to vote Democratic for the past several decades. Since 1948 the county has selected the Democratic Party candidate in 71% of national elections. However, the county swung hard to Donald Trump in 2016, and in 2020 Trump posted the best percentage in the county by a Republican presidential candidate since Theodore Roosevelt in 1904.
United States presidential election results for Day County, South Dakota[22]
