Clay County, South Dakota

Clay County
Clay County Courthouse
Location within the U.S. state of South Dakota
South Dakota's location within the U.S.
Coordinates: 42°54′58.14″N 96°58′49.684″W / 42.9161500°N 96.98046778°W / 42.9161500; -96.98046778
Country United States
State South Dakota
FoundedApril 10, 1862
Named afterHenry Clay
SeatVermillion
Largest cityVermillion
Area
  Total
417.419 sq mi (1,081.11 km2)
  Land412.022 sq mi (1,067.13 km2)
  Water5.397 sq mi (13.98 km2)  1.3%
Population
 (2020)
  Total
14,967
  Estimate 
(2024)
15,245
  Density37.451/sq mi (14.460/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional districtAt-large
Websiteclaycountysd.org

Clay County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 14,967, and was estimated to be 15,245 in 2024. 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, Iowa-SD-Nebraska Combined Statistical Area.