Louisiana Purchase Summary

  • Last updated on November 10, 2022

The single largest land acquisition in U.S. history, the Louisiana Purchase not only doubled the territory of the United States but also secured new western borders for the nation and effectively removed France as a colonial power from North America.

Summary of Event

The first Europeans to explore the region that became known as the Louisiana Territory were the Spanish during the sixteenth century, but they failed to occupy the area effectively. In 1682, the French explorer René Robert Cavelier, sieur de La Salle, claimed the region for France and named it in honor of King Louis XIV. The territory remained French until near the end of the Seven Years’ War (known as the French and Indian War French and Indian War (1754-1763) in North America) in 1763, when France ceded it to Spain Spain;and Louisiana Purchase[Louisiana Purchase] in return for help in France’s war against Great Britain and its allies and to compensate Spain for the loss of Florida. During the late 1790’s, France began to rebuild its empire in the Western Hemisphere. Through the secret Treaty of San Ildefonso San Ildefonso, Treaty of (1800) of October 1, 1800, Spain ceded Louisiana back to France. Louisiana Purchase Napoleon I [p]Napoleon I[Napoleon 01];and Louisiana Purchase[Louisiana Purchase] Jefferson, Thomas [p]Jefferson, Thomas;and Louisiana Purchase[Louisiana Purchase] French Empire;and Louisiana Purchase[Louisiana Purchase] [kw]Louisiana Purchase (May 9, 1803) [kw]Purchase, Louisiana (May 9, 1803) Louisiana Purchase Napoleon I [p]Napoleon I[Napoleon 01];and Louisiana Purchase[Louisiana Purchase] Jefferson, Thomas [p]Jefferson, Thomas;and Louisiana Purchase[Louisiana Purchase] French Empire;and Louisiana Purchase[Louisiana Purchase] [g]Spain;May 9, 1803: Louisiana Purchase[0190] [g]United States;May 9, 1803: Louisiana Purchase[0190] [g]France;May 9, 1803: Louisiana Purchase[0190] [c]Expansion and land acquisition;May 9, 1803: Louisiana Purchase[0190] [c]Diplomacy and international relations;May 9, 1803: Louisiana Purchase[0190] Barbé-Marbois, François de La Salle, Sieur de Livingston, Robert R. Monroe, James [p]Monroe, James;and Louisiana Purchase[Louisiana Purchase] Toussaint-Louverture

Reports of the impending transfer of Louisiana, and perhaps even Florida, from Spain to France began to reach the United States in the spring of 1801. The Jefferson administration viewed this transfer with some alarm, because a powerful and aggressive Napoleonic France in control of the mouth of the Mississippi River would constitute a much graver threat to U.S. rights on that vital artery of commerce and communication than the presence of weak and declining Spain. Spain;and Louisiana Purchase[Louisiana Purchase] Secretary of State James Madison instructed Robert R. Livingston, Livingston, Robert R. the U.S. minister to Paris, to investigate the continuing rumors. If Livingston found them to be true, he was to try to acquire the Floridas Florida;and Louisiana Purchase[Louisiana Purchase] (or at least West Florida) if they were part of the cession. If Spain had not ceded the Floridas to France, the United States would attempt to obtain them from Spain. Livingston learned that France had acquired Louisiana and New Orleans, but not the Floridas. His discussions with the French government were otherwise inconclusive.

The Louisiana Purchase Territory





On October 16, 1802, the Spanish administrator of Louisiana at New Orleans, Juan Ventura Morales Morales, Juan Ventura , issued a proclamation withdrawing from the United States the right to deposit goods at New Orleans for transshipping, as the Pinckney Treaty of 1795 Pinckney’s Treaty (1795)[Pinckneys Treaty] Spain;and Louisiana Purchase[Louisiana Purchase] with Spain had provided. This meant that U.S. boats coming down the Mississippi River could no longer unload their goods at New Orleans for reloading aboard oceangoing vessels sailing to the East Coast and foreign ports. The United States blamed the French for this Spanish edict, although France had not yet taken possession of Louisiana.

When news of the suspension reached westerners who depended on the Mississippi River Mississippi River;and Louisiana Purchase[Louisiana Purchase] and the use of the port of New Orleans New Orleans;and Louisiana Purchase[Louisiana Purchase] as their commercial lifeline, they were greatly aroused, as were their spokespersons in Congress. There was a real possibility that armed westerners might march on New Orleans and seize it. In response to their demands for action to protect U.S. rights on the Mississippi River and at New Orleans, President Thomas Jefferson sent James Monroe Monroe, James [p]Monroe, James;and Louisiana Purchase[Louisiana Purchase] as his envoy to France to help Livingston Livingston, Robert R. in the negotiations with the French government. Livingston and Monroe were authorized to try to acquire, at most, only New Orleans and the Floridas, should they belong to France, and the right of the free navigation of the Mississippi River.

Meanwhile, Napoleon’s plans for restoring the French Empire French Empire;and Canada[Canada] in North America depended on subjugating slaves on the West Indian island of Santo Domingo Santo Domingo;slave rebellion Hispaniola (Hispaniola) who were in revolt under the leadership of Pierre Dominique Toussaint Toussaint-Louverture Louverture. The sugar, coffee, indigo, and cotton produced on that island were important to the French economy, and the island might serve as a staging ground for any projected French invasion of the North American continent. Napoleon realized that if the French could not control the island, Louisiana would be of little value to him. Despite the expenditure of many lives, thousands of French troops, and enormous sums of money, the slaves were far from subdued at the end of 1802, and Santo Domingo was in ruins. Napoleon decided to abandon the island. As Louisiana would have served mainly as a granary and supply region for that island, it would be of little worth to France. Napoleon, therefore, elected to sell Louisiana to the United States.

Napoleon had several other reasons for making the sale. Determined to resume war against Great Britain and other European powers, he needed funds to restock his army after the military debacle in Santo Domingo Santo Domingo . He also feared that Great Britain might simply take Louisiana from France and thought that he could forestall the formation of an alliance between the United States and Great Britain and even perhaps build up the United States as a rival that would check British expansion. He probably also was aware of the difficulties that Spain Spain;and Louisiana Purchase[Louisiana Purchase] had had in dealing with the numerous Native American societies in the region since 1762 and expected that France might have no better luck. Finally, he wished to avert war with an expanding United States, whose government appeared set to empower its president to seize New Orleans by force.

On April 11, 1803, Napoleon ordered his minister of finance, the marquis de Barbé-Marbois, Barbé-Marbois, François de to negotiate the sale of the entire territory of Louisiana, not only New Orleans and its environs. Although they had no authorization to purchase all Louisiana, Livingston Livingston, Robert R. and Monroe Monroe, James [p]Monroe, James;and Louisiana Purchase[Louisiana Purchase] entered into the bargaining and, after some haggling over price, came to terms. The negotiations were completed on May 9, although the treaty and two conventions making up the agreement bore the date April 30. Under the agreement, the United States acquired “Louisiana,” including New Orleans New Orleans;and Louisiana Purchase[Louisiana Purchase] , but its boundaries were only vaguely defined. In return, the United States agreed to pay approximately fifteen million dollars, assume the debts that French citizens owed to the United States (roughly one-quarter of the purchase price), and incorporate all inhabitants of Louisiana—except indigenous peoples and slaves—as citizens of the United States. The news reached the United States around July 4, adding extra jubilation to the patriotic mood on the nation’s independence day.

Although Jefferson had some grave doubts about the constitutionality of the purchase because the Constitution Constitution, U.S.;and Louisiana Purchase[Louisiana Purchase] did not expressly grant the president or Congress the power to acquire foreign territory, he approved it. He mulled over the idea of proposing an amendment to legitimize the purchase and any future territorial acquisition. After further reflection, Jefferson realized that with the exception of a few Federalists who worried that the nation would grow too large for an effective democracy, the majority of both Congress and the people of the United States enthusiastically supported the purchase. Jefferson decided to draw on a so-called “higher laws doctrine” and found enough justification for the purchase in the preamble to the U.S. Constitution, which states as one of its purposes the need to “promote the general Welfare.”

The U.S. Senate ratified the agreements on October 20, and the president proclaimed them to be in effect the next day. The formal transfer of the southern portion of the territory from Spain Spain;and Louisiana Purchase[Louisiana Purchase] to France—despite the Treaty of San Ildefonso San Ildefonso, Treaty of (1800) —occurred on November 30, 1803, and the transfer from France to the United States occurred on December 20. The northern segment was transferred to the United States on March 10, 1804, one day after Spain had returned it to France. A little less than one year after Napoleon had proposed the sale, Louisiana was the property of the United States.


Acquisition of the Louisiana Territory virtually doubled the territorial extent of the United States, giving the new nation what then seemed to be almost limitless room for expansion. It also made possible the nation’s later expansion to the Pacific Ocean. The purchase also set a precedent for obtaining foreign territory and peoples by treaty, and it increased nationalist feelings in the country and helped undercut secessionist intrigues in the West. It did not solve all the problems of the West, but it redirected their nature. Friction with New Spain—which was soon to become Mexico—and the various Great Plains and Texas Native Americans increased, but the French were no longer a complicating factor.

Within a few decades, the new territory would provoke major debates over the future expansion of slavery there and the removal of Native Americans to a newly created Indian Territory. In 1803, the purchase demarcated a reserve for Native Americans west of the Mississippi River and provided a place for the eventual relocation of most eastern tribal peoples in the ensuing four decades. Meanwhile, the federal government undertook to survey the extent of its new territories by having Meriwether Lewis and William Clark lead a major expedition of exploration.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Balleck, Barry J. “When the Ends Justify the Means: Thomas Jefferson and the Louisiana Purchase.” Presidential Studies Quarterly 22, no. 4 (1992): 679-696. Argues that Jefferson’s support of the purchase was consistent with his constitutional views.
  • citation-type="booksimple"

    xlink:type="simple">Carson, David A. “The Role of Congress in the Acquisition of the Louisiana Territory.” Louisiana History 26, no. 4 (1985): 369-383. Asserts that Napoleon was aware of unpassed congressional resolutions to authorize the president to employ force to seize New Orleans.
  • citation-type="booksimple"

    xlink:type="simple">Cerami, Charles A. Jefferson’s Great Gamble: The Remarkable Story of Jefferson, Napoleon, and the Men Behind the Louisiana Purchase. Naperville, Ill.: Sourcebooks, 2003. Admirably clear and engaging history of the Louisiana Purchase that examines all the figures who played a role in that event.
  • citation-type="booksimple"

    xlink:type="simple">Flemingo, Thomas. Louisiana Purchase. New York: John Wiley & Sons, 2003. Brief study of the Louisiana Purchase, emphasizing the diplomatic negotiations, that is well suited for high school students.
  • citation-type="booksimple"

    xlink:type="simple">Kukla, Jon. A Wilderness so Immense: The Louisiana Purchase and the Destiny of America. New York: Alfred A. Knopf, 2003. Beautifully written and well-illustrated scholarly study of the Louisiana Purchase that examines the event from all perspectives.
  • citation-type="booksimple"

    xlink:type="simple">Lyon, E. Wilson. Louisiana in French Diplomacy, 1759-1804. Norman: University of Oklahoma Press, 1934. The second half of the book gives a detailed account of French viewpoints leading to the sale of Louisiana.
  • citation-type="booksimple"

    xlink:type="simple">Peterson, Merrill D. Thomas Jefferson and the New Nation. New York: Oxford University Press, 1970. This spirited interpretation demonstrates that Jefferson was more than a passive player in the negotiations to secure Louisiana.
  • citation-type="booksimple"

    xlink:type="simple">Sheehan, Bernard W. Seeds of Extinction: Jeffersonian Philanthropy and the American Indian. Chapel Hill: University of North Carolina Press, 1973. Places the Louisiana Purchase within the context of Jeffersonian-era attitudes about removal of eastern Native Americans to the West.
  • citation-type="booksimple"

    xlink:type="simple">Skolnik, Richard, comp. 1803: Jefferson’s Decision: The United States Purchases Louisiana. New York: Chelsea House, 1969. Reprints many of the primary sources pertinent to the purchase.

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