The Annexation of California from Mexico

Instructor: Zachary Adams

Zak has taught college-level history and has a master's degree in American history

From 1820 to 1850, five different flags flew over the state of California. Read on to learn how this territory of the Mexican Far North became the west coast of the United States.

California's Five Flags

California is an integral part of the United States, but that wasn't always the case. Inhabited by native people and then colonized by Spain, the state has a deep history with a rapid series of changes in the mid-1800s. By the time it was annexed by the United States, Californian territory had seen five separate flags within the space of a single lifetime. Why? Who was involved?

Let's follow the course of California's annexation through Spain, Mexico, and the United States.

Early Spanish and Mexican History

The Spanish were the first Europeans to settle the land we know as California, where they established ports to resupply ships in the Pacific Ocean and Franciscan missions to both spread religion to California's native people and use them for labor in the cattle industry.

The Spanish called the land Alta California, and their settlers, known as californios, found themselves isolated from the rest of the Spanish Empire even while growing wealthy as merchants and traders in beef, tallow, and cattle hides.

When Mexico gained its independence from Spain in 1821, Alta California was the last to declare its allegiance to the new government. A young californios would have seen fireworks and ceremony, but little enthusiasm from friends and neighbors as a second flag, that of Mexico, flew over the territory.

Under Mexican rule, California remained distant from the capital. However, the Mexican government removed an old Spanish policy prohibiting trade with foreigners so, starting in the 1820s, American, British, and Russian traders and fur trappers landed their ships in California's ports.

Map Showing the Boundaries of Alta California
Map of Mexican Territory

U.S. Interest

Americans also immigrated, drawn by the mild climate and cheap land. By the mid-1830s, the people of the United States began to think seriously about expanding the nation to the Pacific, with President Andrew Jackson proposing that the U.S. purchase San Francisco Bay from Mexico in 1835.

As the United States increasingly embraced the desire of its citizens to move westward, California became a key target of expansion. The californios would have met new neighbors, been able to purchase new goods from across the world, and perhaps noticed the increasing presence of the United States.

The mid-1830s also saw changes in Mexico's government that alienated californios. In 1834 President Antonio López de Santa Anna, the infamous figure of Texas history, shifted the government from federalist to centralist, exerting more control over Mexico's provinces. This upset californios who had been used to ruling themselves, to the point where a revolt broke out.

In 1836, northern leaders declared Californian independence under the Lone Star flag, but southern leaders weren't convinced. Peace prevailed, but not before federalist californios threw out a centralist governor and selected one of their own. They accepted Mexican rule with the caveat of more local control.

The Lone Star flag briefly declaring Californias independence from Mexico
1836 Lone Star Flag

By 1846, hundreds more Americans had moved into California, and the United States and Mexico began posturing towards one another over Texas annexation and the location of Mexico's northern border.

The president of the United States, James K. Polk, had won the 1844 election by campaigning in favor of westward expansion and manifest destiny. This is the idea that the United States was entitled to expand across the North American continent, and he sought to act on that platform.

Polk and the other expansionists eyed California jealously, and hoped to use the opportunity of war with Mexico to annex the land and open it further for American settlers. American forces managed to provoke the Mexican military into conflict in Texas and, on May 13th, 1846, the U.S. declared war with Mexico.

Mexican-American War

In California, the war took on two stages, early success followed by a period of resistance. A month in, an American explorer named John C. Frémont, who had been mapping the region since January, got involved. He led a takeover of the settlement of Sonoma in the name of the independent Bear Republic, the fourth flag to fly over California during the nineteenth century.

One of the flags of the Bear Republic
Bear Republic flag

A few weeks later, the U.S. Navy arrived. Having been stationed in Hawaii to move on California and prevent the British from seizing it, they captured the ports of Monterrey and Yerba Buena (now San Francisco) with ease. Now the stars and stripes flag took over from the Bear Republic.

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