Purcell is a city in McClain County, Oklahoma, United States, and the county seat. As of the 2010 census, the city population was 5,884.Founded in 1887, Purcell was a railroad town named after Edward B. Purcell, who was an official with the Atchison, Topeka and Santa Fe Railway.Purcell is often called the "Quarterhorse Capital of the World" and its official motto is "Heart of Oklahoma"; the city has registered trademarks on both titles.