Mannington is a city in Marion County, West Virginia, United States, located in the hills of North Central West Virginia. The population wa…Mannington is a city in Marion County, West Virginia, United States, located in the hills of North Central West Virginia. The population was 1,961 at the 2020 census. In its earliest years it was called Forks of Buffalo or Koon Town, but has been called Mannington since 1856.