The Umatilla lived in the Umatilla River and adjacent parts of the Columbia River drainages in northeastern Oregon. They now live on the Umatilla Indian Reservation in the same area with the Wallawalla Cayuse. They spoke a Sahaptin language of the Penutian phylum and numbered about one thousand in the 1980s.
Kennedy, James Bradford (1977). "The Umatilla Indian Reservation, 1855-1975: Factors Contributing to a Diminished Land Resource Base." Dissertation Abstracts International 38(4):2344A.
Stern, Theodore (1960). "A Umatilla Prophet Cult." Acts of the International Congress of Anthropological and Ethnological Sciences 5:346-350.