Union County, Illinois

Union County, Illinois
Location within the U.S. state of Illinois
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 
(2024)
16,886
 • Density41.8/sq mi (16.1/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".