The Louisiana Purchase (French: Vente de la Louisiane, lit. 'Sale of Louisiana') was the acquisition of the territory of Louisiana by the United States from the French First Republic in 1803. This consisted of most of the land in the Mississippi River's drainage basin west of the river. In return for fifteen million dollars, or approximately eighteen dollars per square mile ($7/km2), the United States nominally acquired a total of 828,000 sq mi (2,140,000 km2; 530,000,000 acres) of land now in the Central United States. However, France only controlled a small fraction of this area, most of which was inhabited by Native Americans; effectively, for the majority of the area, the United States bought the preemptive right to obtain Indian lands by treaty or by conquest, to the exclusion of other colonial powers.
The Kingdom of France had controlled the Louisiana territory from 1682 until it was ceded to Spain in 1762. In 1800, Napoleon Bonaparte, the First Consul of the French Republic, regained ownership of Louisiana in exchange for territories in Tuscany as part of a broader effort to re-establish a French colonial empire in North America. However, France's failure to suppress a revolt in Saint-Domingue in the Caribbean, coupled with the prospect of renewed warfare with the United Kingdom, prompted Napoleon to consider selling Louisiana to the United States.
Acquisition of Louisiana was a long-term goal of President Thomas Jefferson, who was especially eager to gain control of the crucial Mississippi River port of New Orleans. Jefferson tasked James Monroe and Robert R. Livingston with purchasing New Orleans. Negotiating with French Treasury Minister François Barbé-Marbois, the U.S. representatives quickly agreed to purchase the entire territory of Louisiana after it was offered. Overcoming the opposition of the Federalist Party, Jefferson and Secretary of State James Madison persuaded Congress to ratify and fund the Louisiana Purchase.
The Louisiana Purchase extended United States sovereignty across the Mississippi River, nearly doubling the nominal size of the country. The purchase included land from fifteen present U.S. states and two Canadian provinces, including the entirety of Arkansas, Missouri, Iowa, Oklahoma, Kansas, and Nebraska; large portions of North Dakota and South Dakota; the area of Montana, Wyoming, and Colorado east of the Continental Divide; the portion of Minnesota west of the Mississippi River; the northeastern section of New Mexico; northern portions of Texas; New Orleans and the portions of the present state of Louisiana west of the Mississippi River; and small portions of land within Alberta and Saskatchewan. At the time of the purchase, the territory of Louisiana's non-native population was around 60,000 inhabitants, of whom half were enslaved Africans. The western borders of the purchase were later settled by the 1819 Adams–Onís Treaty with Spain, while the northern borders of the purchase were adjusted by the Treaty of 1818 with the British.
The Louisiana Purchase corresponds, nowadays, to more than 26% of the present area of the contiguous United States, which is 2,959,064.44 square miles (7,663,941.7 km2).
Throughout the second half of the 18th century, the French colony of Louisiana became a pawn for European political intrigue. The colony was the most substantial presence of France's overseas empire, though its population was sparse and largely concentrated in small settlements along the Mississippi River and its tributaries. France ceded the territory to Spain in 1762 in the secret Treaty of Fontainebleau. Following French defeat in the Seven Years' War, Spain gained control of the territory west of the Mississippi, and the British received the territory to the east of the river.
Following the establishment of the United States, the Americans controlled the area east of the Mississippi and north of New Orleans. The main issue for the Americans was free transit of the Mississippi out to sea. As the lands were being gradually settled by American migrants, many Americans, including Jefferson, assumed that the territory would be acquired "piece by piece". The risk of another power taking it from a weakened Spain made a "profound reconsideration" of this policy necessary.
New Orleans was already important for shipping agricultural goods to and from the areas of the United States west of the Appalachian Mountains. Pinckney's Treaty, signed with Spain on October 27, 1795, gave American merchants "right of deposit" in New Orleans, granting them use of the port to store goods for export. The treaty also recognized American rights to navigate the entire Mississippi, which had become vital to the growing trade of the western territories.
In 1798, Spain revoked the treaty allowing American use of New Orleans, greatly upsetting the Americans. In 1801, Spanish Governor Don Juan Manuel de Salcedo took over from the Marquess of Casa Calvo, and restored the American right to deposit goods. However, in 1800, Spain had ceded the Louisiana territory back to France as part of Napoleon's secret Third Treaty of San Ildefonso. The subsequent 1801 Treaty of Aranjuez established that Spain's cession of Louisiana was a "restoration" of the territory to France, not a retrocession. The territory nominally remained under Spanish control, until a transfer of power to France on November 30, 1803, just three weeks before the formal cession of the territory to the United States on December 20, 1803.
While the treaty between Spain and France went largely unnoticed in 1800, fear of an eventual French invasion spread across America when, in 1801, Napoleon sent a military force to nearby Saint-Domingue. Though Jefferson urged moderation, Federalists sought to use this against Jefferson and called for hostilities against France. Undercutting them, Jefferson threatened an alliance with Britain, although relations were uneasy in that direction. In 1801, Jefferson supported France in its plan to take back Saint-Domingue (present-day Haiti), which was then under control of Toussaint Louverture after a slave rebellion. However, there was a growing concern in the U.S. that Napoleon would send troops to New Orleans after quelling the rebellion. In hopes of securing control of the mouth of the Mississippi, Jefferson sent Livingston to Paris in 1801 with the authorization to purchase New Orleans.
In December 1801, France sent General Charles Leclerc, Napoleon's brother-in-law, on an expedition to Saint-Domingue to reassert French control over the colony, which had become essentially autonomous under Louverture. Louverture, as a French general, had fended off incursions from other European powers, but had also begun to consolidate power for himself on the island. Before the revolution, France had derived enormous wealth from Saint-Domingue at the cost of the lives and freedom of the enslaved. Napoleon wanted the territory's revenues and productivity for France restored. Alarmed over the French actions and its intention to re-establish an empire in North America, Jefferson declared neutrality in relation to the Caribbean, refusing credit and other assistance to the French, but allowing war contraband to get through to the rebels to prevent France from regaining a foothold.
In 1803, Pierre Samuel du Pont de Nemours, a French nobleman, began to help negotiate with France at the request of Jefferson. Du Pont was living in the United States at the time and had close ties to Jefferson as well as the prominent politicians in France. He engaged in back-channel diplomacy with Napoleon on Jefferson's behalf during a visit to France and introduced the idea of the much larger Louisiana Purchase as a way to defuse potential conflict between the United States and Napoleon over North America.
Throughout this time, Jefferson had up-to-date intelligence on Napoleon's military activities and intentions in North America. Part of his evolving strategy involved giving du Pont some information that was withheld from Livingston. Intent on avoiding possible war with France, Jefferson sent James Monroe to Paris in 1803 to negotiate a settlement, with instructions to go to London to negotiate an alliance if the talks in Paris failed. Spain procrastinated until late 1802 in executing the treaty to transfer Louisiana to France, which allowed American hostility to build. Also, Spain's refusal to cede Florida to France meant that Louisiana would be indefensible.