Sumner is a town in Tallahatchie County, Mississippi. The population was 407 at the 2000 census. Sumner is one of the two county seats of Tallahatchie County. It is located on the west side of the county and the Tallahatchie River, which runs through the county north–south. The other county seat is Charleston, located east of the river. Charleston was the first county seat, as settlement came from the east, and it is the larger of the two towns.