The story of the Louisiana Purchase begins, improbably, with burning fields of Haitian sugar cane.
In 1791, taking advantage of divisions among colonial rulers created by the roiling French Revolution, slaves on the French Caribbean island colony of Saint-Domingue (today's Haiti) rose up en masse, launching the only successful slave rebellion in recorded human history. Theirs was no small accomplishment; at the time sugar was one of the world's most valuable commodities, and Saint-Domingue was the greatest producer of sugar in the world. The slaves, who burned down the cane fields, freed their neighbors, and organized themselves into ferocious armies under skilled leaders like Toussaint Louverture, eventually defeated not only French but also British and Spanish military efforts to reimpose the slave regime. By 1804, the slaves had gained complete control of the island, declaring independence and thereby transforming Saint-Domingue, the crown jewel of the French colonial empire, into Haiti, the world's first black republic.
The Haitians' unlikely success proved to be a huge boon to American aspirations for transcontinental expansion. Before 1803, the United States spread not from sea to shining sea, but only as far west as the banks of the Mississippi River. The vast territory to the west belonged to France. But when the Haitians defeated a French expeditionary army in 1802, they ended French Emperor Napoleon Bonaparte's dream of a new French empire in North America. Napoleon had hoped to use the Louisiana Territory—not just today's state of Louisiana, but the entire watershed of the Missouri River, stretching from the Gulf of Mexico to the crest of the Rocky Mountains—to provide food and supplies to the sugar factories on Saint-Domingue. Without Saint-Domingue and its immense sugar profits, Napoleon had no use for Louisiana, and in 1803 he offered to sell it to the United States.
For a cost of $15 million—less than 3 cents an acre—the United States instantly doubled in size.
American President Thomas Jefferson dispatched a Corps of Discovery, led by Meriwether Lewis and William Clark, to explore the new lands and plot a navigable course from the Missouri to the Pacific. The Lewis & Clark expedition's two-year journey from St. Louis to the mouth of the Columbia River and back—one of the great feats of exploration in our history—solidified American claims not only to Louisiana but also to the Oregon Territory of the Pacific Northwest. But Lewis & Clark's mission was much more than a feat of navigation; it was one of the great scientific accomplishments of the Age of Enlightenment. Following detailed instructions from Thomas Jefferson himself, Lewis & Clark became diplomats, anthropologists, botanists, zoologists, meteorologists, and geologists—collecting in their journals an incredible trove of information on the land and the people, plants, and animals they found in it.
Taken together, the Louisiana Purchase and Voyage of Discovery are usually remembered as an unmitigated triumph for the United States and for Thomas Jefferson—a shrewd real estate purchase combined with a courageous feat of exploration to help make Jefferson's vision of a transcontinental American "empire of liberty" a reality. However, the Purchase also created intractable new political problems for the Republic. Jefferson himself believed the Purchase was unconstitutional, and his expedient decision to go through with it anyway aggrandized executive power in a way that undermined Jefferson's own democratic political philosophies.
Even more troubling in the long term, the Louisiana Purchase created half a century of sectional conflict, as southern slave states and northern free states jockeyed to impose their respective labor systems on the new territories. The new states that eventually emerged from the Purchase—thirteen of them, from Louisiana to Montana—would hold the balance of power between slave and free, and the competing partisans of slavery and free labor struggled mightily to impose their respective systems on the new states. Most of the mileposts that marked the country's dark journey toward Civil War related to the question of slavery in the Louisiana Purchase—the Missouri Compromise, the Kansas-Nebraska Act, and the Dred Scot Supreme Court decision.