Purchased in 1803 from France for $15 million –about four cents per acre–the Louisiana Purchase added much of the Great Plains to the United States, set the stage for expansion to the Pacific Ocean, and set in motion sectional conflicts over slavery that led to the Civil War.
The territory of Louisiana comprised a significant region of the interior of North America. Its borders were the Mississippi River on the east, the Rocky Mountains on the west, and the Spanish territories of Texas and New Mexico on the south, but the northern border was never clearly defined (although it roughly followed the forty-ninth parallel). Louisiana Territory– under French, Spanish, and American possession–was mainly occupied by Native American peoples until the 1850s. European settlement was limited to river towns (for example, New Orleans and St. Louis) and trading posts along the Mississippi and Missouri Rivers. Until 1763 France controlled most of Louisiana Territory, although Spain intruded on several occasions, including the 1720 Pedro de Villazur expedition into present-day Nebraska. France transferred Louisiana to Spain in 1763 after being defeated in the French and Indian War (Seven Years War in Europe). By the early 1790s the fledgling United States, which was expanding westward toward the Mississippi, relied on the river and the port of New Orleans as an outlet for trans-Appalachian produce. A 1795 treaty with Spain guaranteed Americans access to New Orleans, but by 1801 that privilege was threatened when Spain gave Louisiana back to France. Napoleon hoped to use Louisiana as a base to reestablish its colonial empire in the Caribbean and possibly in North America.
Fearing that access to New Orleans might be blocked by the French presence, President Thomas Jefferson sought to buy or negotiate access to a Mississippi port. In January of 1803 James Monroe traveled to Paris with instructions to offer $2 million for New Orleans and West Florida. Fortunately for the United States, their offer came on the heels of French setbacks in the Caribbean (malaria and yellow fever had ravaged the French military) and the threat of war with England. Fearing that Louisiana would be lost to a British-American alliance, and in need of money to launch further military campaigns, Napoleon ordered his minister to sell all of Louisiana to the American negotiators. The agreed-upon price, $15 million ($11,250,000 for Louisiana and $3,750,000 for American civilian claims against France), gave the United States approximately 828,000 square miles of territory, nearly doubling the land base of the nation. The Senate approved the deal on October 20, 1803.
Exactly what the United States had purchased remained unclear. When asked by Monroe about the boundaries, the French foreign minister responded: "You have made a noble bargain for yourselves, and I suppose you will make the most of it." The Lewis and Clark expedition (1804-6) did just that. The expedition, which wintered near the mouth of the Columbia River in 1805-6, pushed the boundaries of Louisiana beyond the Rocky Mountains to the Pacific Ocean, giving the United States a claim to Oregon. The southern boundary was more difficult to discern, because Spain occupied neighboring Texas and New Mexico. The Adams-Onis Treaty of 1819 finally set the southern boundary at the western bank of the Sabine, Red, and Arkansas Rivers.
The Louisiana Purchase eventually added thirteen states to the nation and brought the Great Plains–America's future breadbasket– into the nation. The purchase also had unforeseen consequences as it sowed the seeds of sectionalism over the expansion of slavery.
Mark R. Ellis University of Nebraska at Kearney
DeConde, Alexander. This Affair of Louisiana. New York: Scribner, 1976.
Hermann, Binger. The Louisiana Purchase. Washington DC: Government Printing Office, 1898.