Spain opened an overland route from Sonora to California in 1774, but Yuma Indians closed it in 1781. Mexico attempted to reopen the route in 1822. Lieutenant Romualdo Pacheco and soldiers built an adobe fort at this site in 1825-26, the only Mexican fort in Alta California. On April 26, 1826, Kumeyaay Indians attacked the fort, killing three soldiers and wounding three others. Pacheco abandoned the fort and removed the soldiers to San Diego.