Indian Territory, in U.S. history, name applied to the country set aside for Native Americans by the Indian Intercourse Act (1834). In the 1820s, the federal government began moving the Five Civilized Tribes (Cherokee, Creek, Seminole, Choctaw, and Chickasaw) of the Southeast to lands W of the Mississippi River. The Indian Removal Act of 1830 gave the President authority to designate specific lands for them, and in 1834 Congress formally approved the choice. The Indian Territory included present-day Oklahoma N and E of the Red River, as well as Kansas and Nebraska; the lands were delimited in 1854, however, by the creation of the Kansas and Nebraska territories. Tribes other than the original five also moved there, but each tribe maintained its own government. As white settlers continued to move westward, pressure to abolish the Indian Territory mounted. With the opening of W Oklahoma to whites in 1889 the way was prepared for the extinction of the territory, achieved in 1907 with the entrance of Oklahoma into the Union.