Clark County, Illinois

Clark County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 39°20′N 87°47′W / 39.33°N 87.79°W / 39.33; -87.79
Country United States
State Illinois
Founded1819
Named afterGeorge Rogers Clark
SeatMarshall
Largest cityMarshall
Area
  Total
505 sq mi (1,310 km2)
  Land501 sq mi (1,300 km2)
  Water3.4 sq mi (9 km2)  0.7%
Population
 (2020)
  Total
15,455
  Estimate 
(2023)
15,088
  Density31/sq mi (12/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional district12th
Websitewww.clarkcountyil.org

Clark County is a county located in the southeastern part of U.S. state of Illinois, along the Indiana state line. As of the 2020 census, the population was 15,455. Its county seat is Marshall. The county was named for George Rogers Clark, an officer who served in the American Revolution.