Unable to maintain his authority in the self-proclaimed "Republic of Lower California," William Walker is driven from Mexico and taken into custody by the U.S. military. (By Brian Bockelman)

On the run from Mexican troops, William Walker and his fellow filibusters left Baja California for Sonora, a neighboring Mexican state. (By Brian Bockelman)

American filibuster William Walker proclaims himself president of an independent "Republic of Lower California," encompassing the two northern Mexican states of Baja California and Sonora. (By Brian Bockelman)

Determined to spread the "manifest destiny" of U.S. expansion southward into Latin America, a young American adventurer named William Walker and 45 followers invaded Baja California, in northwestern Mexico. (By Brian Bockelman)

Ill with dysentery and harassed by Mexican troops, Gaston Raousset departed Sonora for San Francisco, bringing to a close his first filibustering expedition to Mexico. (By Brian Bockelman)

Mexican troops expelled Gaston Raousset and his filibusters from Hermosillo, the capital of the northern Mexican state of Sonora. (By Brian Bockelman)

When Governor Fernando Cubillas of Sonora (Mexico) demands that French adventurer Gaston Raousset and his followers adopt Mexican citizenship or leave the country, Raousset declares Sonora to be an independent republic. (By Brian Bockelman)

French filibuster Gaston Raoul Raousset, along with 600 mercenary troops recruited in San Francisco, arrived in the northern Mexican state of Sonora. His intent was to capture territory on behalf of a Franco-Mexican mining company. (By Brian Bockelman)