Cayuse Indians, a tribe of the Waiilatpuan language family, distantly related to the Nez Percé. Originally the Cayuse were a seminomadic tribe that ranged over the dry uplands of eastern Oregon and Washington. They became famous as horse breeders, and “cayuse” became synonymous with “Indian pony.” Their numbers were estimated at 500 in the late 18th century. In 1847, resentful of the growing number of settlers on their lands, they destroyed the Marcus Whitman mission in Washington. The so-called Cayuse War followed. Eventually they were forced to settle on the Umatilla reservation in Oregon. Many present-day Cayuse still reside on or near the reservation.