Despite its status as a department of Mexico, Alta California was without a strong presence of Mexican authority. Instead, power was welded by shifting alliances among the local families, who were California-born but of Spanish blood, and who considered themselves distinct from Mexicans. These "Californio" families -- the Peraltas, Sepulvedas, Picos, Yorbas, Figueroas, Castros, Carrillos, Vallejos and others -- drew their wealth from their vast land holdings: General Mariano Vallejo, for example, in 1846 had a private estate of over 175,000 acres.

By the 1840s, the Californios had come to realize their days as the ruling power were numbered. In 1844, the United States had elected James K. Polk as President on a platform that espoused "Manifest Destiny" -- the expansion of the U.S. to its "natural" western boundary of the Pacific ocean. American warships were frequent visitors to Alta California ports -- particularly Monterey, the departmental capital. Added to these threats was the simmering dispute between the U.S. and Mexico over Texas. British and French ambitions in the Pacific also concerned the Mexicans as did the expansion of Russian power from Alaska.

The Californios were well aware of their region's history: the Native Americans had been conquered by the Spanish, who in turn lost their power to the Mexicans in the secularization of the missions. Furthermore, the Californios knew that just as Mexico's hold was weakening, so would theirs. The time was right, many felt, for a new power to rise in California. But, they differed as to which power it should be. Pio Pico, the Mexican governor, favored the British, who had promised to send Irish settlers ousted from their homeland; the Irish would at least be Catholic like the Californios. Others, like General Vallejo, were weary of monarchs -- British, Spanish, French, or otherwise -- and favored the United States.