Fayette County, Illinois

Fayette County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 39°00′N 89°01′W / 39°N 89.02°W / 39; -89.02
Country United States
State Illinois
Founded1821
Named afterMarquis de Lafayette
SeatVandalia
Largest cityVandalia
Area
  Total
725 sq mi (1,880 km2)
  Land716 sq mi (1,850 km2)
  Water8.9 sq mi (23 km2)  1.2%
Population
 (2020)
  Total
21,488
  Estimate 
(2023)
21,164
  Density30/sq mi (11/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional district15th
Websitewww.fayettecountyillinois.gov

Fayette County is a county located in the U.S. state of Illinois. As of the 2020 census, the population was 21,488. Its county seat is Vandalia, the site of the Vandalia State House State Historic Site. Ramsey Lake State Recreation Area is located in the northwestern part of this county.