Union County, Illinois

Union County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 37°28′N 89°16′W / 37.47°N 89.26°W / 37.47; -89.26
Country United States
State Illinois
FoundedJanuary 2, 1818
SeatJonesboro
Largest cityAnna
Area
  Total
422 sq mi (1,090 km2)
  Land413 sq mi (1,070 km2)
  Water8.7 sq mi (23 km2)  2.1%
Population
 (2020)
  Total
17,244
  Estimate 
(2023)
16,667
  Density41/sq mi (16/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional district12th
Websitewww.unioncountyil.gov

Union County is a county located in the U.S. state of Illinois. According to the 2020 United States census, it had a population of 17,244. Its county seat is Jonesboro. It is located in the southern portion of Illinois known locally as "Little Egypt".