These two online resources, Ancestry Library Edition and Fold3, are excellent starting points for genealogical research in this area of study.
Ancestry Library Edition provides access to census records for selected Native American Tribes, U.S. Indian Wills archives, Index to Indian War Affidavits for selected states and the U.S. School Yearbooks for Native Americans for selected years.
Fold3 includes historical primary documents featuring U.S. city directories, naturalization records, and Revolutionary War Pensions. Collections include Native American Archives.
White Buffalo, Cheyennes, from the Photos - Native Americans (Rinehart) Collection in Fold3