Basically the tribes were coerced by violence to relocate to Indian Territory. Some tribes were able to hide out and they later became their own tribes in their original homelands. Famous examples include the Poarch Band of Creek Indians of Alabama, Seminole Tribe of Florida (who were never militarily defeated by the United States), Sac & Fox Tribe of the Mississippi in Iowa, and Mississippi Band of Choctaw Indians.

A band of Nez Perce were forced from Washington to Indian Territory in 1878. Basically they said hell no and returned back to the NW in 1884. Same with the Northern Cheyenne, who returned to Montana on foot in the winter of 1878.

The Dawes Commission, led by Senator Henry L. Dawes (still hated today by most Oklahoma Indians), oversaw destroying tribal governments and landholdings in Indian Territory. The Curtis Act of 1898 dismantled tribal governments, courts, and school systems (many of these buildings were stolen from the tribes). The Dawes Severalty Act called for lands collectively owned by the tribes to be broken up into small individual allotments to individual Indians and Freedmen/Freedwomen. Then the so-called "Surplus" land was opened up to non-Native settlements in lotteries and land runs.

When the idea of combining Oklahoma Territory, Indian Territory, and the "unassigned lands" was proposed, traditionalists fought it legally and even by force (see the Four Mother's Society, the Green Peach War). Politicians from the NE tribes tried to promise a separate State of Sequoyah to be separate from Oklahoma (it breaks my heart that this didn't happen).

Some tribes have recovered stolen public buildings from the state of Oklahoma in recent years. The tribes had to reorganized their governments under the Oklahoma Indian Welfare Act of 1936 and rebuild their infrastructure in ensuing decades. Some have repurchased important lands, but compensation, no.