Clinton County, Illinois

Clinton County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 38°37′N 89°25′W / 38.61°N 89.42°W / 38.61; -89.42
Country United States
State Illinois
Founded1824
Named afterDeWitt Clinton
SeatCarlyle
Largest cityBreese
Area
  Total
503 sq mi (1,300 km2)
  Land474 sq mi (1,230 km2)
  Water29 sq mi (80 km2)  5.8%
Population
 (2020)
  Total
36,899
  Estimate 
(2023)
36,785
  Density73/sq mi (28/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional district12th
Websiteclintonco.illinois.gov

Clinton County is a county located in the U.S. state of Illinois. At the 2020 census, the population was 36,899. Its county seat is Carlyle. In 1960, the United States Census Bureau placed the mean center of U.S. population in Clinton County. Clinton County is part of the St. Louis, MO-IL Metropolitan Statistical Area.