Bear Flag Revolt
When war became likely in 1846 between the United States and Mexico, U.S. Army Major John C. Frémont, who had arrived in California claiming to be on a mission to find a route to the Pacific (his mission officially was to find the source of the Arkansas River), began encouraging a rebellion among the Anglo-American settlers. As a result, thirty-three settlers in Sonoma broke free and raised a homemade flag with a bear and star (the "Bear Flag") to symbolize their taking control. The words "California Republic" appeared on the flag but were never officially adopted by the insurgents. Their actions were later called the "Bear Flag Revolt."John Sutter joined the rebellion by opening the doors of Sutter's Fort
The same day, the rebels captured the Commandant of Northern California, General Mariano Guadalupe Vallejo, who openly endorsed the inevitability of the annexation of California by the United States. Vallejo was sent to Sutter's Fort, where he was kept a prisoner until August 1, 1846. The Republic's first and only president was William B. Ide, whose rule lasted twenty-five days. On June 23, 1846, Frémont arrived with sixty soldiers and took command in the name of the United States. The Bear Flag was replaced by the Stars and Stripes. The "republic" vanished and Ide enlisted in the U.S. forces as a private. The Mexican governor sent 55 men to attempt to crush the rebellion, but General José Castro's forces were defeated at the Battle of Olompali.
Unknown to Frémont and the Bear Flag supporters, war had already been formally declared on May 13, 1846, but the news did not reach California until early July, when the frigate USS Savannah and the two sloops, USS Cyane and USS Levant, of the United States Navy captured Monterey, California.
 Bear FlagThe original Bear Flag, photographed in 1890. Digital reproduction based on the original Bear Flag Modern flag of the State of California, for comparison
The most notable legacy of the "California Republic" was the adoption of its flag as the basis of the modern state Flag of California. The modern flag has a star, a grizzly bear, and a colored stripe with the words "California Republic". The Sonoma Plaza, site of the raising of the original Bear Flag, is marked by a California Historical Landmark.
The original Bear Flag was designed and made by William L. Todd, who was a first cousin of Mary Todd Lincoln, wife of president Abraham Lincoln. Todd painted the flag on domestic cotton cloth, roughly a yard and a half in length. It featured a red star based on the California Lone Star Flag that was flown during California's 1836 revolt led by Juan Alvarado and Isaac Graham. The flag also featured an image of a grizzly bear en statant (standing). The modern flag shows the bear en passant (walking).
The original Bear Flag was destroyed in the fires following the 1906 San Francisco earthquake. A replica, created in 1896 for the 50th Anniversary celebrations, is on display at the Presidio de Sonoma, which was established in 1836 by Mariano Guadalupe Vallejo as a part of Mexico's attempt to halt Russian incursions into the region.
 Proclamation of the Bear Flag Revolt
William B. Ide wrote a proclamation of independence on the night of June 14–15, 1846, and read it on the fifteenth:
To all persons, citizens of Sonoma, requesting them to remain at peace, and to follow their rightful occupations without fear of molestation.
– William B. Ide, Head Quarters Sonoma, June 15, 1846