The United States and California
The Mexican government and Spanish-speaking Californians became increasingly suspicious of the motives of the "Americans" of the United States. In 1844, John Charles Frémont led a party of Army topographical engineers that "accidentally" crossed the Sierras into California and traveled the length of the San Joaquin Valley before making their way home. In 1845, a commodore in the U.S. Navy, misinformed about relations between his country and Mexico, sailed into Monterey Harbor and declared a victory in a non-existent war. Frémont returned in December 1845, ostensibly to survey the passes through the Sierras being used by American emigrant trains.
Thus Frémont and his sixty armed scouts and soldiers were at hand in the spring of 1846 when rumors circulated of imminent war between Mexico and the United States. On June 10, Americans near Sonoma took up arms and declared an independent California Republic with a homemade flag bearing a single star and the painted image of a grizzly, thus earning their uprising the name of the Bear Flag Revolt. Frémont joined the rebels in their short-lived republic, which ended on July 9, when the Americans learned that their nation and Mexico were officially at war and that an American battleship lay in Monterey Harbor. Frémont and his men enlisted in the official military operations, and the California Republic ceased to exist.
There were many hard-fought battles with Mexican troops and Californian ranchers on one side and American soldiers and settlers on the other before the Mexican War in California ended in the Americans' favor with the Cahuenga Capitulation in January 1847. Before the end of that month, a battalion of Mormons who had enlisted in the Army in Iowa arrived. In March, they were joined by 1,000 members of a regiment from New York who also arrived to fight a war that was over. However, as the Mormons were bound to join Brigham Young and his colony, now located in Utah, and as most of the New Yorkers had enlisted with the promise that they could remain in California after the war, they were not disappointed to miss the fighting.
They were content to bide their time acquainting themselves with the newest part of the United States. The territory of Alta California was then home to 150,000 indigenous peoples and 14,000 inhabitants of European and Mexican descent. Most of the surviving native tribes and clans lived in the mountainous north where the mission fathers had not spread Christianity and European diseases, while most of these 14,000 newcomers lived in the south, clustered around Monterey and Los Angeles. There were Europeans in the north, some living in the tiny trading community of Yerba Buena, recently rechristened San Francisco, and others clustered around Sutter's fort on the Sacramento. All realized that United States government would bring great changes, but none could have anticipated just how quickly those changes would come.