Susceptible to Seizure
In centuries past, and as global knowledge expanded in the Age of Sail, any attractive land that was scantily occupied and poorly defended was ripe for takeover by a more powerful nation—regardless of the acknowledged ownership claims of another.
California is a case in point. Spain held it for 300 years; Spain's successor Mexico ruled the province for another twenty-five. Neither expended much effort to develop its potential. Each was fearful of outside conquest, yet both lacked the resources to promote more than minimal colonization, or install adequate military defenses.
In 1812 the Russians brazenly established Fort Ross north of Bodega Bay, when Spain was too weak to evict them. Not long after Mexico acquired Spain’s former New World territories in 1822, a French sea captain expressed astonishment that what he saw as a beautiful, fertile, easily-taken California, had not already become the prey of other Old World powers. The British were somewhat interested, but as the developers and overlords of the vast Oregon Territory to the north, weren’t yet ready to pounce.
Meanwhile East Coast American seafaring merchants engaged in California’s hide and tallow trade were bringing back reports of its unexploited resources and balmy climate, raising interest in Washington D.C. Richard Henry Dana’s widely-read Two Years Before the Mast, a memoir based on the diary Dana kept while at sea and published in 1840, further influenced thinking with its detailed account of life on the California coast. Throughout the early 1840s, Americans migrating West chose Oregon, jointly held by England and the USA, as their destination; and in smaller numbers California, despite its being foreign country. The Californios themselves (Mexican citizens born in California) grew weary of obedience-without-benefit to rulers in far off Mexico City, many favoring complete independence, or acquisition by another nation, with England and America the most popular choices, though there were some who favored France.
American interest in California reached its official zenith when “dark horse” candidate James K. Polk was sworn in as President of the United States in 1845. His ambitious expansionist platform, and firm personal resolve, was to admit Texas to the Union (accomplished in December 1845); dissolve the arrangement whereby England and America jointly held the Oregon Territory (accomplished in June 1846); and to acquire California so that the North American continent would be one nation from sea to sea.
President Polk accomplished this by winning the Mexican-American War, originally declared because of a dispute over the southern Texas-Mexico border. In February 1848, the Treaty of Guadalupe Hidalgo ceded California and today’s American Southwest to the victorious Yankees.