History - Native American: Websites
Museums
The National Museum of the American Indian is the first national museum dedicated to the preservation, study, and exhibition of the life, languages, literature, history, and arts of Native Americans. 
Tamastslikt Cultural Institute. Tamastslikt is a musem and cultural center near Pendleton, associated with a gambling casino. Definitely worth a visit.
Websites
The National Archives site includes a digital collection, genealogical resources, and tribal resources, among other things.
Confederated Tribes of the Umatilla Indian Reservation. The Cayuse, Umatilla and Walla Walla tribes all share this reservation.
Nez Perce National Historical Park. One of the services of the National Park Service.
Oregon Historical Society publication "Oregon is Indian Country" gives an overview of our tribes.
American Indians fo the Pacific Northwest. A joint project of the Library of Congress and the University of Washington, it has over 2000 photographs, information on treaties, ceremonial dress, and the Annual Reports of the Commissioner of Indian Affairs from 1851-1908. An example is below, showing Willamette Falls (Oregon City) in 1841.