Hardin, OhioHardin is an unincorporated community in Shelby County, in the U.S. state of Ohio.HistoryHardin was platted in 1816. The community was named for John Hardin, a Continental Army officer in the American Revolutionary War. who was killed on this site in 1792. Hardin was the county seat from 1819 until 1820. A post office called Hardin was established in 1820, and discontinued in 1909.