city, seat (1907) of Carter county, southern Oklahoma, U.S., north of the Red River, near Lake Texoma and the Texas state line. Founded in 1887 in Chickasaw Indian Territory after the arrival of the Atchison, Topeka and Santa Fe Railroad (Atchison, Topeka and Santa Fe Railway Company, The), the town was named for the Philadelphia suburb that was the home of a railroad official. Populated by African Americans, Native Americans, and whites in roughly equal numbers, it developed as the business centre of a large cattle and farming region and grew rapidly after the discovery of oil nearby in 1905. Much of the original town was destroyed and some 50 people killed in 1915 when a gasoline tanker exploded.

Oil refining, manufacturing, ranching, tourism, and wholesaling are the major economic activities of the city. Ardmore is the site of Carter Seminary (formerly Bloomfield Academy, founded 1848), a boarding school for Indian children now operated by the Chickasaw Nation (Chickasaw), and of the Greater Southwest Historical Museum. Lake Murray State Park, the Chickasaw National Recreation Area (embracing Arbuckle Mountains), and the Gene Autry Oklahoma Museum are nearby. Inc. chartered city 1898; city, 1959. Pop. (1990) 23,079; (2000) 23,711.