Illinois Counties
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Illinois Counties

There are one hundred and two counties in Illinois. St. Clair County was the first county established in what is today Illinois. Most counties in Illinois were named after early American leaders, especially of the American Revolutionary War, as well as soldiers from the Battle of Tippecanoe and the War of 1812.

Union County, Illinois

Union County Education, Geography, and History

Union County, Illinois CourthouseUnion County is a county located in the state of Illinois. According to the 2010 census, it had a population of 17,808. Union County was created on January 2, 1818. The county seat is Jonesboro. The county is named for the federal union of the United States.

Etymology - Origin of Union County Name

The county is named for the federal union of the United States.


County QuickFacts: CensusBureau Quick Facts

Union County History

Union County was created on January 2, 1818 (Territorial Laws, 1817-1818, p. 15) and was formed from Johnson and Jackson Counties . Present area, or parts of it, formerly included in: Johnson County (1812-1818), Randolph County (1795-1812) and St. Clair County (1790-1795).

The County was named for the federal union of the American States. The County Seat is Jonesboro (1818-Present).

Geography: Land and Water

As reported by the Census Bureau, the county has a total area of 422 square miles (1,093 km2), of which, 416 square miles (1,078 km2) of it is land and 6 square miles (15 km2) of it (1.41%) is water.

Union county is located in south Illinois. Trail of Tears State Forest and Union County State Fish and Wildlife Area are located in this county.

Neighboring Counties

Bordering counties are as follows:

  • Northeast: Williamson County
  • East: Johnson County
  • Southeast: Pulaski County
  • South: Alexander County
  • Southwest: Cape Girardeau County, Mo.
  • Northwest: Perry County, Mo.; Jackson County


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