Newcastle is a city in McClain County, Oklahoma, United States and part of the Oklahoma City Metropolitan Area. The population is approx 7,685. Newcastle lay in the Chickasaw Nation. The community's first residents included Choctaw, Chickasaw, and individuals who had married into those tribes. Many were involved in ranching. By 1907, the community had a subscription school, a cotton gin, two stores, and two blacksmiths.