William Walker's filibustering retreat to Sonora, 1854

Background. In the summer of 1853, William Walker traveled to Guaymas seeking a grant from the Mexican government to establish a colony that would serve as a fortified frontier. Motivated by earlier filibustering projects, he organized unauthorized military expeditions into Mexico with the intention of establishing colonies. On October 15, 1853, Walker set out with forty-five men to conquer the Mexican territories of Baja California and Sonora, initiating the conflict that led to his eventual retreat.

Establishment of the Republic. Walker declared independence from Mexico on January 10, 1854, establishing the Republic of Sonora. He placed Baja California under the laws of the American state of Louisiana, where slavery remained legal; the territory was later pronounced part of the larger Republic of Sonora. The republic was ruled by Walker as a short-lived, unrecognized federal entity. His actions generated interest in San Francisco, where bonds for the Republic of Sonora were sold, and its flag was raised in various places.

Retreat and Collapse. The enterprise suffered from a lack of supplies and discontent from within, and the Mexican government quickly forced Walker to retreat. He was soon driven back to California by the Mexican forces. This military pressure resulted in the collapse of the short-lived republic he had established, ending Walker's initial filibustering attempt in northern Mexico.