Settlement of Oregon did not directly raise the issue of slavery. But the nation’s acquisition of part of Mexico did. When Mexico achieved its independence from Spain in 1821 it was nearly as large as the United States and its population of 6.5 million was about two-thirds that of its northern neighbor. Mexico’s northern provinces—California, New Mexico, and Texas— however, were isolated and sparsely settled outposts surrounded by Indian country. New Mexico’s population at the time of Mexican independence consisted of around 30,000 persons of Spanish origin, 10,000 Pueblo Indians, and an indeterminate number of “wild” Indians—nomadic bands of Apaches, Comanches, Navajos, and Utes. With the opening in 1821 of the Santa Fe Trail linking that city with Independence, Missouri, New Mexico’s commerce with the United States eclipsed trade with the rest of Mexico.

California’s non-Indian population in 1821, some 3,200 missionaries, soldiers, and settlers, was vastly outnumbered by about 20,000 Indians living and working on land owned by religious missions and by 150,000 members of unsubdued tribes in the interior. In 1834, in the hope of reducing the power of the Catholic Church and attracting Mexican and foreign settlers to California, the Mexican government dissolved the great mission landholdings and emancipated Indians working for the friars. Most of the land ended up in the hands of a new class of Mexican cattle ranchers, the Californios, who defined their own identity in large measure against the surrounding Indian population. Californios referred to themselves as gente de razon (people capable of reason) as opposed to the indios, whom they called gente sin razon (people without reason). For the “common good,” Indians were required to continue to work for the new landholders.

A watercolor of a scene on a ranch near Monterey, California, in 1849 depicts Californios supervising the work of Native Americans.

Westward migration in the early and mid-1840s took American settlers across Indian country into the Oregon Territory, ownership of which was disputed with Great Britain. The Mormons migrated west to Salt Lake City, then part of Mexico.

By 1840, California was already linked commercially with the United States. New England ships were trading with the region, as illustrated in Richard Henry Dana’s popular novel Two Years before the Mast (1840), an account of a young man’s voyage to California and his experiences there. California also attracted a small number of American newcomers. In 1846, Alfred Robinson, who had moved from Boston, published Life in California. “In this age of annexation,” he wondered, “why not extend the ‘area of freedom’ by the annexation of California?”

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