Hardin County was established by Kentucky's First Legislature in 1792. It was named for Colonel John Hardin, an officer in the Continental Army. The county, when formed, contained 7,000 square miles. All or part of the following counties were formed of territory which originally was contained in Hardin County: Breckinridge, Grayson, Green, Ohio, Meade, LaRue, Daviess, Hancock, Henderson, McLean, Hart, Edmonson, and Butler.
Today Hardin County consists of 616 square miles with a population of 105,543 as determined by the 2010 U.S. Census.