Constituent state of the United States of America. In its land and its people, Oklahoma is a state of contrast and of the unexpected. The terrain varies from the rolling, timbered hills of the east, where the state borders Missouri and Arkansas, to the treeless high plains that extend into Texas and New Mexico to the west. Oklahoma's east central region is dominated by the lowlands of the Arkansas River, sweeping in from Colorado and Kansas on the north, and by the Red River, which forms nearly all of its southern border with Texas. Oklahoma covers an area of 69,956 square miles (181,186 square kilometres). The capital is Oklahoma City.
The word Oklahoma is derived from two Choctaw Indian words: okla, “people,” and humma, “red.” During the 19th century the future state was a symbol of one of the least glorious chapters in American history, becoming known as Indian Territory, the dumping ground for Indian tribes displaced by white settlers' ever-increasing hunger for land. Since its admission in 1907 as the 46th state of the Union, however, Oklahoma has achieved an integration of its Indian citizens into modern economic and social life that probably is unmatched by any other state. There is no reservation in the usual sense for the Indian population. Though numbers of “blanket Indians” may possess no more than their bedrolls, others have risen to positions of distinction. Manyshare in the great wealth that oil resources have brought to the state.