The time before and after the turn of the century sees the application of assimilation policies. Reservations are changed by proclamation, and the implementation of allotment brings fundamental changes to the physical, legal, political, and cultural landscapes.
Native sovereignty is further diminished by the Supreme Court, which grants Congress the authority to unilaterally change any treaty provisions.
After World War I, the Snyder Act and the Citizenship Act begin a process of recognizing on one hand the continued existence of Native peoples and on the other of integrating them legally into the United States.
These processes were helped by Native peoples themselves, who are beginning a process of creating opportunities to have their voices heard.