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. Some are named after natural features or counties in other states. Some are named for early Illinois leaders. Two counties are named for Native American tribes, and one bears the name of a plant used as a food-source by Native Americans.
Even though Illinois does not have a Lincoln County named after its favorite son, Abraham Lincoln, it does have a Douglas County named after his political rival Stephen A. Douglas. It also has Calhoun County, named after John C. Calhoun, outspoken for his southern views in the years preceding the American Civil War. Many of the counties are named after Southerners, reflecting the fact that Illinois was for a short time part of Virginia, and settled in its early years by many southerners. No counties are named after Northern heroes of the Civil War, mainly because the counties were almost all named before that War. The State even has a Lee County named after the family of Robert E. Lee, who at one time served in Illinois. Illinois also has a singular distinction of having two counties named after the same person (DeWitt Clinton).
Information on the FIPS county code, county seat, year of establishment, origin, etymology, population, area and map of each county is included in the table below.
Note: the links in the FIPS County Code column are to the Census Bureau info page for that county.