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Clay County, South Dakota facts for kids

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Clay County
Clay County Courthouse
Clay County Courthouse
Map of South Dakota highlighting Clay County
Location within the U.S. state of South Dakota
Map of the United States highlighting South Dakota
South Dakota's location within the U.S.
Country  United States
State  South Dakota
Founded 1862
Named for Henry Clay
Seat Vermillion
Largest city Vermillion
 • Total 417 sq mi (1,080 km2)
 • Land 412 sq mi (1,070 km2)
 • Water 5.1 sq mi (13 km2)  1.2%
 • Total 14,967
 • Estimate 
15,150 Increase
 • Density 35.89/sq mi (13.858/km2)
Time zone UTC−6 (Central)
 • Summer (DST) UTC−5 (CDT)
Congressional district At-large

Clay County is a county in the U.S. state of South Dakota. As of the 2020 United States Census, the population was 14,967. The county seat is Vermillion, which is also home to the University of South Dakota. The county is named for Henry Clay, American statesman, US Senator from Kentucky, and United States Secretary of State in the 19th century.

Clay County comprises the Vermillion, SD Micropolitan Statistical Area, which is also included in the Sioux City-Vermillion, IA-SD-NE Combined Statistical Area.


Clay County began forming in 1859 when the land was opened for legal occupation. In the fall of that year, Ahira A. Partridge (who would later become the first elected sheriff of the county) crossed the Missouri river into the Dakota territory, and became the first white man to settle what would become Clay county; squatting on 160 acres of land that encompass most of the present-day city of Vermillion. In 1862 the county was formally organized. The Clay County Courthouse was built in 1912.

Clay County is the name of 17 other counties in the United States, most of them named in honor of Henry Clay.


According to the U.S. Census Bureau, the county has a total area of 417 square miles (1,080 km2), of which 412 square miles (1,070 km2) is land and 5.1 square miles (13 km2) (1.2%) is water. It is the smallest county by area in South Dakota.

Protected areas

Adjacent counties


Historical population
Census Pop.
1870 2,621
1880 5,001 90.8%
1890 7,509 50.1%
1900 9,316 24.1%
1910 8,711 −6.5%
1920 9,654 10.8%
1930 10,088 4.5%
1940 9,592 −4.9%
1950 10,993 14.6%
1960 10,810 −1.7%
1970 12,923 19.5%
1980 13,689 5.9%
1990 13,186 −3.7%
2000 13,537 2.7%
2010 13,864 2.4%
Est. 2021 15,150 9.3%
US Decennial Census
1790-1960 1900-1990
1990-2000 2010-2020

2010 census

As of the 2010 census, there were 13,864 people, 5,110 households, and 2,628 families in the county. The population density was 33.6 inhabitants per square mile (13.0/km2). There were 5,639 housing units at an average density of 13.7 per square mile (5.3/km2). The racial makeup of the county was 91.1% White, 3.1% American Indian, 1.7% Asian, 1.3% black or African American, 0.5% from other races, and 2.3% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population. In terms of ancestry, 43.9% were German, 16.4% were Norwegian, 15.8% were Irish, 8.7% were English, 5.4% were Swedish, and 1.8% were American.

Of the 5,110 households, 24.7% had children under the age of 18 living with them, 40.9% were married couples living together, 7.3% had a female householder with no husband present, 48.6% were non-families, and 32.4% of all households were made up of individuals. The average household size was 2.28 and the average family size was 2.91. The median age was 25.0 years.

The median income for a household in the county was $37,198 and the median income for a family was $61,159. Males had a median income of $37,059 versus $28,016 for females. The per capita income for the county was $19,518. About 8.0% of families and 24.0% of the population were below the poverty line, including 13.6% of those under age 18 and 6.7% of those age 65 or over.

Racial/ethnic makeup

The racial makeup of the county was 92.78% White, 1.00% Black or African American, 2.66% Native American, 1.95% Asian, 0.01% Pacific Islander, 0.29% from other races, and 1.31% from two or more races. 0.89% of the population were Hispanic or Latino of any race. 32.0% were of German, 15.6% Norwegian, 9.9% Irish and 5.4% English ancestry.


From 2000 Census data, over 50% consider themselves "unclaimed".




Unincorporated communities


The county is divided into twelve townships:

  • Bethel
  • Fairview
  • Garfield
  • Glenwood
  • Meckling
  • Norway
  • Pleasant Valley
  • Prairie Center
  • Riverside
  • Spirit Mound
  • Star
  • Vermillion


  • University of South Dakota - In 1862 the territorial legislature located the State University in Vermillion, but nothing was done until 1882 when Clay County voted $10,000 in bonds to construct a building on its campus.
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