The Cayuse (Wailatpa, Wailatpu) lived around the heads of the Wallawalla, Unatilla, and Grand Ronde rivers and extended from the Blue Mountains to Deschutes River in the general area of Pendleton and La Grande in northeastern Oregon. They spoke a language isolate in the Penutian phylum and probably number about three hundred today on the Umatilla Indian Reservation in Oregon, where they live among the Wallawalla and Umatilla.
Ruby, Robert H., and John A. Brown (1972). The Cayuse Indians: Imperial Tribesmen of Old Oregon. Norman: University of Oklahoma Press.