Lat/Long: 39.5833, -88.6000
Sullivan, Illinois, is the county seat of Moultrie County, Illinois. In March 1839, the U.S. Post Office Department established a post office in the area that would become Sullivan, naming the post office East Nelson. In 1844, Moultrie County officials presented an area that would become Sullivan, then known as Asa's Point, as one of three possible locations for the permanent seat of government for the county. The voters selected Asa's Point, and in August 1845, the Post Office Department changed the name of the local post office from East Nelson to Sullivan. County officials named the town after Sullivan's Island in the harbor of Charleston, South Carolina, which General William Moultrie, namesake of the county, defended during the American Revolution.
Combined History of Shelby and Moultrie Counties, Illinois (Philadelphia: Brink & McDonough, 1881), 67; Edward Callary, Place Names of Illinois (Urbana and Chicago: University of Illinois Press, 2009), 339; James N. Adams, comp., Illinois Place Names (Springfield: Illinois State Historical Society, 1989), 519.