On the eve of the American Revolution, Spain sought to control the Pacific coast of today's United States against British and Russian incursions. Juan Bautista de Anza, a third-generation frontier soldier of New Spain, shepherded 198 emigrants and their escorts and 1,000 head of livestock on the first overland colonizing expedition from Sonora, Mexico into Alta, or Upper, California. This expedition led to the founding of the Presidio of San Francisco and missions San Francisco de Asís (Mission Dolores) and Santa Clara de Asís.
Anza's expedition and the route it established are commemorated by the Juan Bautista de Anza National Historic Trail.