In 1803, President Thomas Jefferson purchased the territory of Louisiana from the French government for $15 million. The Louisiana Purchase stretched from the Mississippi River to the Rocky Mountains and from Canada to New Orleans, and it doubled the size of the United States. To Jefferson, westward expansion was the key to the nation’s health: He believed that a republic depended on an independent, virtuous citizenry for its survival, and that independence and virtue went hand in hand with land ownership, especially the ownership of small farms. (“Those who labor in the earth,” he wrote, “are the chosen people of God.”) In order to provide enough land to sustain this ideal population of virtuous yeomen, the United States would have to continue to expand. The westward expansion of the United States is one of the defining themes of 19th-century American history, but it is not just the story of Jefferson’s expanding “empire of liberty.” On the contrary, as one historian writes, in the six decades after the Louisiana Purchase, westward expansion “very nearly destroy[ed] the republic.”
Manifest Destiny
By 1840, nearly 7 million Americans–40 percent of the nation’s population–lived in the trans-Appalachian West. Following a trail blazed by Lewis and Clark, most of these people had left their homes in the East in search of economic opportunity. Like Thomas Jefferson, many of these pioneers associated westward migration, land ownership and farming with freedom. In Europe, large numbers of factory workers formed a dependent and seemingly permanent working class; by contrast, in the United States, the western frontier offered the possibility of independence and upward mobility for all. In 1843, one thousand pioneers took to the Oregon Trail as part of the “Great Emigration.”
Did you know? In 1853, the Gadsden Purchase added about 30,000 square miles of Mexican territory to the United States and fixed the boundaries of the “lower 48” where they are today.
In 1845, a journalist named John O’Sullivan put a name to the idea that helped pull many pioneers toward the western frontier. Westward migration was an essential part of the republican project, he argued, and it was Americans’ “manifest destiny” to carry the “great experiment of liberty” to the edge of the continent: to “overspread and to possess the whole of the [land] which Providence has given us,” O’Sullivan wrote. The survival of American freedom depended on it.
Westward Expansion and Slavery
Meanwhile, the question of whether or not slavery would be allowed in the new western states shadowed every conversation about the frontier. In 1820, the Missouri Compromise had attempted to resolve this question: It had admitted Missouri to the union as a slave state and Maine as a free state, preserving the fragile balance in Congress. More important, it had stipulated that in the future, slavery would be prohibited north of the southern boundary of Missouri (the 36º30’ parallel) in the rest of the Louisiana Purchase.
However, the Missouri Compromise did not apply to new territories that were not part of the Louisiana Purchase, and so the issue of slavery continued to fester as the nation expanded. The Southern economy grew increasingly dependent on “King Cotton” and the system of forced labor that sustained it. Meanwhile, more and more Northerners came to believed that the expansion of slavery impinged upon their own liberty, both as citizens–the pro-slavery majority in Congress did not seem to represent their interests–and as yeoman farmers. They did not necessarily object to slavery itself, but they resented the way its expansion seemed to interfere with their own economic opportunity.
Westward Expansion and the Mexican War
Despite this sectional conflict, Americans kept on migrating West in the years after the Missouri Compromise was adopted. Thousands of people crossed the Rockies to the Oregon Territory, which belonged to Great Britain, and thousands more moved into the Mexican territories of California, New Mexico and Texas. In 1837, American settlers in Texas joined with their Tejano neighbors (Texans of Spanish origin) and won independence from Mexico. They petitioned to join the United States as a slave state.