Indian Territory and the Indian Territories are terms that generally described an evolving land area set aside by the United States government for the relocation of Native Americans who held original Indian title to their land as an independent nation. The concept of an Indian territory was an outcome of the U.S. federal government's 18th- and 19th-century policy of Indian removal. After the American Civil War (1861–1865), the policy of the U.S. government was one of assimilation.
Indian Territory later came to refer to an unorganized territory whose general borders were initially set by the Nonintercourse Act of 1834, and was the successor to the remainder of the Missouri Territory after Missouri received statehood.