19th century

Imperial Russia explored the California coast and established a trading post at Fort Ross. Its early 19th-century coastal settlements north of San Francisco Bay constituted the southernmost Russian colony in North America and were spread over an area stretching from Point Arena to Tomales Bay.^[33]
In 1821, the Mexican War of Independence gave Mexico (including California) independence from Spain; for the next 25 years, Alta California remained a remote northern province of the nation of Mexico.
Cattle ranches, or ranchos, emerged as the dominant institutions of Mexican California. After Mexican independence from Spain, the chain of missions became the property of the Mexican government and were secularized by 1834.^[34] The ranchos developed under ownership by Californios (Spanish-speaking Californians) who had received land grants, and traded cowhides and tallow with Boston merchants.
From the 1820s, trappers and settlers from the United States and Canada arrived in Northern California. These new arrivals used the Siskiyou Trail, California Trail, Oregon Trail and Old Spanish Trail to cross the rugged mountains and harsh deserts in and surrounding California.
Between 1831 and 1836, California experienced a series of revolts against Mexico;^[35] this culminated in the 1836 California revolt led by Juan Bautista Alvarado, which ended after Mexico appointed him governor of the department.^[36] The revolt, which had momentarily declared California an independent state, was successful with the assistance of American and British residents of California,^[37] including Isaac Graham;^[38] after 1840, 100 of those residents who did not have passports were arrested, leading to the Graham affair in 1840.^[37]
One of the largest ranchers in California was John Marsh. After failing to obtain justice against squatters on his land from the Mexican courts, he determined that California should become part of the United States. Marsh conducted a letter-writing campaign espousing the California climate, soil and other reasons to settle there, as well as the best route to follow, which became known as "Marsh's route." His letters were read, reread, passed around, and printed in newspapers throughout the country, and started the first wagon trains rolling to California.^[39] He invited immigrants to stay on his ranch until they could get settled, and assisted in their obtaining passports.^[40]
After ushering in the period of organized emigration to California, Marsh helped end the rule of the last Mexican governor of California, thereby paving the way to California's ultimate acquisition by the United States.^[41]
In 1846, settlers rebelled against Mexican rule during the Bear Flag Revolt. Afterwards, rebels raised the Bear Flag (featuring a bear, a star, a red stripe and the words "California Republic") at Sonoma. The Republic's only president was William B. Ide,^[42] who played a pivotal role during the Bear Flag Revolt.