Mansfield is a village in Piatt County, Illinois in the United States. The population was 906 at the 2010 census. Mansfield was originally incorporated around 1870. The village may have been named for John Mansfield, an officer in the Civil War. Other sources suggest Mansfield was named after a number of other unrelated men named Mansfield, …Mansfield is a village in Piatt County, Illinois in the United States. The population was 906 at the 2010 census. Mansfield was originally incorporated around 1870. The village may have been named for John Mansfield, an officer in the Civil War. Other sources suggest Mansfield was named after a number of other unrelated men named Mansfield, including Jared Mansfield, an early American surveyor, or J.L. Mansfield, a local philanthropist. The village may also have been named after the city of Mansfield, Ohio – which was itself named for the surveyor Jared Mansfield.