State (pop., 2000: 3,450,654), U.S., southwest-central region.
Bordered by Colorado, Kansas, Missouri, Arkansas, Texas, and New Mexico, it covers 69,903 sq mi (181,049 sq km). Its capital is Oklahoma City . The Red River forms its southern boundary; the Arkansas River flows across northeastern Oklahoma. Its highest point is Black Mesa (4,973 ft [1,516 m]), located in the Panhandle. Evidence of inhabitation by the Folsom cultures, 15,000–10,000 years ago, has been found. In more modern times, until the expedition of Francisco Vázquez de Coronado in 1541, the area was home to representatives of at least three major Indian language groups. Spanish control of the area lasted until 1800, when it passed to the French. In 1803 the area became part of the U.S. with the {{link=Louisiana Purchase">Louisiana Purchase . In 1828 the U.S. Congress reserved Oklahoma for settlement by Indians, and it became known as Indian Territory . In 1890 the western part was organized as Oklahoma Territory. The two were merged and admitted to the union as the 46th state in 1907. Cattle raising and farming are the mainstays of the economy. Mineral products include natural gas, petroleum, coal, and stone. The state's heritage is reflected in Indian and cowboy museums. A barge system links the state's second major city, Tulsa , to the Gulf of Mexico.