Williamson is a city in and the county seat of Mingo County, West Virginia, United States, situated along the Tug Fork River. The population wa…Williamson is a city in and the county seat of Mingo County, West Virginia, United States, situated along the Tug Fork River. The population was 3,042 at the 2020 census. and is the county's largest and most populous city. Williamson is home to Southern West Virginia Community and Technical College. The Tug Fork River separates Williamson from South Williamson, Kentucky.