Winfield is a city in and the county seat of Putnam County, West Virginia, United States, located along the Kanawha River. The population wa…Winfield is a city in and the county seat of Putnam County, West Virginia, United States, located along the Kanawha River. The population was 2,397 at the 2020 census. It is part of the Huntington–Ashland metropolitan area.