The Confederated Tribes of the Umatilla Reservation, composed of the Umatilla, Cayuse, and Walla Walla tribes, combined to form a single tribal government in 1949, nearly a hundred years after the groups collectively ceded several million acres of land to the U.S. government. Today the 172,000-acre reservation, bordered by Pendleton to the west and the Umatilla National Forest to the east, has about 2,800 tribal members. One of the major economic ventures undertaken by
the tribe is the Wildhorse Resort and Casino and Tamástslikt Cultural Institute, found 6 miles east of Pendleton, near the reservation's westernmost edge.
Bounded by I–84, Hwy. 11 (to Athena), and the Umatilla National Forest. There is also a smaller section south of I–84. The reservation's tribal headquarters are in Mission, 6 miles east of Pendleton, 46411 Ti'imine Way, Pendleton, Oregon, 97801, United States