Jersey County, Illinois

Jersey County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 39°05′N 90°22′W / 39.09°N 90.36°W / 39.09; -90.36
Country United States
State Illinois
FoundedFebruary 28, 1839
Named afterNew Jersey
SeatJerseyville
Largest cityJerseyville
Area
  Total
377 sq mi (980 km2)
  Land369 sq mi (960 km2)
  Water7.9 sq mi (20 km2)  2.1%
Population
 (2020)
  Total
21,512
  Density57/sq mi (22/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional district15th
Websitewww.jerseycounty-il.us

Jersey County is a county located in the U.S. state of Illinois. At the 2020 census, it had a population of 21,512. The county seat and largest community is Jerseyville, with a population of 8,337 in 2010. The county's smallest incorporated community is Otterville, with a population of 87.

Jersey County is included in the St. Louis, MO-IL Metropolitan Statistical Area.