Mendenhall is a city and the county seat of Simpson County, Mississippi, United States. The population was 2,504 at the 2010 census. Mende…Mendenhall is a city and the county seat of Simpson County, Mississippi, United States. The population was 2,504 at the 2010 census. Mendenhall is part of the Jackson Metropolitan Statistical Area. Mendenhall was originally called Edna, to honor the wife of developer Phillip Didlake. After learning that a town with that name already existed in Mississippi, the city had its name changed to Mendenhall to honor Thomas Mendenhall, a citizen and lawyer from Westville, Mississippi.