Winfield is a town in Putnam County, West Virginia, United States, along the Kanawha River. The population was 2,301 at the 2010 census. It is the county seat of Putnam County.Winfield is a part of the Huntington-Ashland, WV-KY-OH, Metropolitan Statistical Area. As of the 2010 census, the MSA had a population of 287,702. New definitions from February 28, 2013 placed the population at 363,000.