The Confederated Tribes of the Umatilla Indian Reservation is a federally recognized confederation of three Sahaptin-speaking Native American tribes who traditionally inhabited the Columbia River Plateau region: the Cayuse, Umatilla, and Walla Walla. When the leaders of the Walla Walla, Cayuse, and Umatilla peoples signed a treaty with the United States in 1855, they ceded 6.4 million acres of homeland in what is now northeastern Oregon and southeastern Washington. Today the three-tribe confederation numbers 2,652. Roughly half of the tribal population live on or near the reservation, which is also home to about 300 Indians enrolled with other Tribes, such as the Yakama, Tenino (Warm Springs), and Nez Perce, as well as 1,500 non-Indians. The tribes share the Umatilla Indian Reservation...'
Contributions by Parkwells, Valfontis, and Decumanus.