Origins of the Mexican War; or, the fight for the Pacific Coast

Welcome to our series on the Mexican War. Rather than outline the events of the war itself, which are easily found in many other places, we’ll focus here on the less well-known aspects of that war, the drivers and the players who, in different ways, brought the war on and saw it through.

The Mexican War (1846-8) is often seen today as a major example of U.S. western expansion at all costs, at the expense of Mexico alone. While there were many Americans at the time who believed in the nation’s Manifest Destiny—its right and even its duty to expand across the continent and take possession of it—the situation surrounding the Mexican War, American motives and actions leading to that war, and the nations involved were more complex than they seem.

Mexico was going through tremendous upheaval at the time. In 1846 four different presidencies took office. Democratic Mexican self-government was hampered by a colonial history which left few Mexicans with the experience or understanding of democratic self-government. Internal revolutions convulsed the nation and made it very difficult for the Mexican government to exert control over its northern territories, particularly Texas, which was quickly filling up with American citizens who, over the course of the 1830s, began to see themselves as citizens of an independent republic.

Most Americans, however, when they looked west, were far more interested in California than Texas. “Upper California” was the territory that is now most of the State of California (“Lower California” being what is now the Baja peninsula in Mexico), and it was considered the finest land in the west. Upper California was part of Mexico, but it was part of the expansion plans of the United States, Great Britain, and Russia.

Each of these nations wanted to claim the entire Pacific Coast, from the Arctic Circle to the present-day U.S.-Mexican border, for itself. Russia had been enjoying a lucrative fur-trading industry on the Pacific Coast since the early 1700s, with trading posts established from Alaska to just north of San Francisco. Alaska was shown on maps as “Russian America.” For Russia, taking control of Upper California from Mexico would be the first, most important step in taking control over its entire fur trading territory. Great Britain of course controlled Canada as a colony, and had an established presence north of the modern-day border of Washington State. But many Britons wanted to seize the Oregon Territory, which was tentatively claimed by the United States, extending British Canada right down to the border with Mexico (the present-day northern border of California).

A map of the Pacific Coast in 1846 would show Alaska as Russian America, with British Canada to its south, extending to its modern border with the State of Washington, a “disputed zone” that is today’s Washington and Oregon south of that, and Mexico (today’s California) south of that. There was no official U.S. presence at all on the Pacific Coast—no U.S. state or territory from the Arctic Circle to modern-day Mexico. There were American citizens living in Upper California, but their population was dwarfed by that of the native Mexicans.

But the U.S. wanted Upper California, and the Oregon Territory (today’s States of Washington and Oregon), and many Americans set out for both destinations in anticipation of U.S. annexation at some point. While Americans in Texas fought their own war against Mexico, it would be the Oregon Territory that first pushed the U.S. itself toward war in the west.

Next time: Fifty-four forty or fight!

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