Linguistically, about two thousand years seem to separate the Kumeyaay from the Quechan on the Colorado River. Some archaeologists recognize a gradual material culture change from 5000 B.C. to that recognized as "Diegueño" by 100 B.C. Mythology and southern band territories suggest that the ancestors of some Kumeyaays were there by 5000 to 8000 B.C. At contact, tribal neighbors in Baja California were speakers of Yuman languages: Cochimi, Kiliwa, Paipai, and Cocopa; to the east were Quechan and Mohave. On the north, Takic-speaking Shoshonean peoples entered about two thousand years ago, Luiseño on the coast, Cupeño at Warner Springs, and Cahuilla in the mountains and desert. Relations with neighbors alternated between war, trade, intermarriage, and ceremonial exchange.
In 1769, continuous contact with Europeans began when Franciscans founded San Diego Mission with a military post, San Diego Presidio. Soon after, Dominicans established missions in northern Baja California. Except for the 1818 foundation of Santa Ysabel Assistancia, Spanish and Mexicans controlled only coastal and near-coastal areas. Raids, Revolts, and fugitivism characterized Kumeyaay-mission relations. Unlike other missions, San Diego and San Luis Rey kept only unmarried women, the sick, and the elderly at the missions owing to lack of agricultural land nearby. They brought in a group, taught them Catholicism, European agriculture, and crafts, and then returned them to the village Except for labor drafts and special ceremonies. After mission secularization, most Kumeyaay fled and revolted, holding Mexicans to the coast.
America's entrance in 1846 did not cause much land loss until the Civil War ended. The few 1875 executive order Reservations were insecure until trust-patented in 1891, when additional lands were reserved for some villages. By then, most were pushed to dry slopes above their original well-watered agricultural valleys. Many received no reservation: some took refuge in a cemetery, Jamul, receiving federal recognition in 1976, and others fled to Baja California, where non-Indian settlers did not crowd them until after 1940.