California Republic The California Republic ( in Spanish " " República de California " " ) , also Bear Flag Republic or Bear Republic , refers to a period of revolt by American settlers in the Mexican territory of Alta California against Mexico . Revolt was initially proclaimed in Sonoma on June 14 , 1846 , before news of the outbreak of the Mexican – American War had reached the area . Although participants declared independence from Mexico , they failed to form a functional provisional government . Thus , the " republic " never exercised any real authority , and it was never recognized by any nation . In fact , most of Alta California knew nothing about it . The revolt lasted 26 days , at the end of which the U . S . Army arrived to occupy the area . Once the leaders of the revolt knew the United States was claiming the area , they disbanded their " republic " and supported the U . S . federal effort to annex Alta California . The California Republic is notable for creation of the " ( Grizzly ) Bear Flag " , whose symbols were later incorporated into the California state flag — including the words " California Republic . " Bear Flag Revolt . U . S . Army Major John C . Frémont 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 ) , he began encouraging a parallel rebellion among the Anglo - American settlers . As a result , thirty - three settlers in Sonoma , assisted by volunteers from among the American settlers and Vacqueros from the many haciendas in the Sacramento River valley , captured the Mexican garrison of Sonoma 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 . " As part of the Sonoma garrison , the rebels captured the Commandant of Northern California , General Vallejo , who openly endorsed the inevitability of the annexation of California by the United States . Vallejo was sent to Sutter ' s Fort in the Sacramento River valley , where he was kept a prisoner until August 1 , 1846 . The Republic ' s first and only president was William B . Ide , whose administration 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 " disbanded 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 Flag . 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 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 the cousin of Mary Todd Lincoln , wife of future American 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 " statant " ( standing , see right ) . The modern flag shows the bear " 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 of Sonoma . 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 :