Hardin County is a county in the U.S. state of Illinois. According to the 2020 census, it has a population of 3,649,[1] making it the least populous county in Illinois. The county seat is Elizabethtown.[2]
Hardin County was founded in 1839 and named for Hardin County, Kentucky, which was named in honor of Colonel John Hardin, an officer in the American Revolutionary War and the Northwest Indian War.