Winfield is a city and county seat of Cowley County, Kansas, United States. It is situated along the Walnut River in South Central Kansas. As of the 2010 census, the city population was 12,301 and second most populous city of Cowley County. Winfield was founded in 1870.] It was named for Rev. Winfield Scott, who promised to build the town a church in exchange for the naming rights. The first post office at Winfield was established in May,1870. In 1873, Winfield incorporated as a city.