Winfield is a city located in the U.S. state of Kansas. It is within and the county seat of Cowley County on the Walnut River in South Central Kansas. It has a total area of 12.93 square miles at 37°14′23″N 96°59′44″W. The elevation is 1,129 feet above sea level. As of the 2010 census data, it had a total population of 12,301. The population density was 950/sq mi. It has Zip code 67156.