Humanities › History & Culture The Louisiana Purchase The Great Bargain That Doubled the Size of the United States Share Flipboard Email Print Getty Images History & Culture American History America Moves Westward Basics Important Historical Figures Key Events U.S. Presidents Native American History American Revolution The Gilded Age Crimes & Disasters The Most Important Inventions of the Industrial Revolution African American History African History Ancient History and Culture Asian History European History Genealogy Inventions Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By Robert McNamara History Expert Robert J. McNamara is a history expert and former magazine journalist. He was Amazon.com's first-ever history editor and has bylines in New York, the Chicago Tribune, and other national outlets. our editorial process Robert McNamara Updated December 31, 2019 The Louisiana Purchase was the enormous land deal in which the United States, during the administration of Thomas Jefferson, purchased territory from France comprising the present-day American Midwest The significance of the Louisiana Purchase was enormous. In one stroke, the young United States had doubled its size. The acquisition of land made westward expansion feasible. And the deal with France guaranteed that the Mississippi River would become a major artery for American commerce, which provided a considerable boost to the economic development of the United States. At the time the deal was struck, the Louisiana Purchase was controversial. Jefferson and his representatives were well aware that the Constitution did not give the president any authority to make such a deal. Yet the opportunity had to be taken. To some Americans, the deal seemed like a treacherous abuse of presidential power. The Congress, also well aware of apparent Constitutional problems, could have moved to derail Jefferson's deal. Yet the Congress approved it. A remarkable aspect of the Louisiana Purchase is that it stands as perhaps Jefferson's greatest accomplishment during his two terms in office, yet he had not even been trying to buy that much land. He was only hoping to acquire the city of New Orleans, but the French emperor, Napoleon Bonaparte, was prompted by circumstances to offer the Americans a far more attractive deal. Background of the Louisiana Purchase At the beginning of Thomas Jefferson's administration, there was great concern in the American government about control of the Mississippi River. It was obvious that access to the Mississippi, and especially the port city of New Orleans, would be vital to the further development of the American economy. In a time before canals and railroads, it was desirable that goods intended to be exported abroad could travel down the Mississippi to New Orleans. As Jefferson took office in 1801, New Orleans belonged to Spain. However, the vast Louisiana territory was in the process of being ceded from Spain to France. And Napoleon had ambitious plans to create a French empire in America. Napoleon's plans unraveled when France had lost its grip on its colony of Saint Domingue (which became the nation of Haiti after a revolt by enslaved people brought from Africa). Any French holdings in North America would be difficult to defend. Napoleon reasoned that he would likely lose that territory as he anticipated war with Britain, and he knew the British would probably dispatch a considerable military force to seize France's holdings in North America. Napoleon decided to offer to sell France's territory in North America to the United States. On April 10, 1803, Napoleon informed his finance minister that he would consider selling all of Louisiana. Thomas Jefferson had been thinking of a much more modest deal. He wanted to buy the city of New Orleans just to ensure American access to the port. Jefferson dispatched James Monroe to France to join the American ambassador, Robert Livingston, in an effort to purchase New Orleans. Before Monroe even arrived in France, Livingston had been informed that the French would consider selling all of Louisiana. Livingston had started negotiations, which Monroe joined. Communication across the Atlantic was very slow at the time, and Livingston and Monroe had no chance to consult with Jefferson. But they recognized that the deal was simply too good to pass up, so they proceeded on their own. They had been authorized to spend $9 million for New Orleans and agreed to spend approximately $15 million for the entire Louisiana territory. The two diplomats assumed that Jefferson would agree that it was a remarkable bargain. The Cession of Louisiana Treaty was signed by the American diplomats representatives of the French government on April 30, 1803. News of the deal reached Washington, D.C., in mid-May 1803. Jefferson was conflicted as he realized he had gone beyond explicit powers in the Constitution. Yet he convinced himself that as the Constitution gave him the power to make treaties, he was within his right to make the enormous purchase of land. The U.S. Senate, which has the power to approve treaties, did not challenge the legality of the purchase. The senators, recognizing a good deal, approved the treaty on October 20, 1803. The actual transfer, a ceremony at which the land became American territory, took place at the Cabildo, a building in New Orleans, on December 20, 1803. Impact of the Louisiana Purchase When the deal was finalized in 1803, many Americans, including especially government officials, were relieved because the Louisiana Purchase ended the crisis over control of the Mississippi River. The enormous acquisition of land was viewed as a secondary triumph. The purchase, however, would have a huge effect on America's future. In total, 15 states, in whole or in part, would be carved out of the land acquired from France in 1803: Arkansas, Colorado, Idaho, Iowa, Kansas, Louisiana, Minnesota, Missouri, Montana, Oklahoma, Nebraska, New Mexico, North Dakota, South Dakota, Texas, and Wyoming. While the Lousiana Purchase came as a surprising development, it would profoundly change America, and help to usher in the era of Manifest Destiny. Sources: Kastor, Peter J. "Louisiana Purchase." Encyclopedia of the New American Nation, edited by Paul Finkelman, vol. 2, Charles Scribner's Sons, 2006, pp. 307-309. Gale eBooks. "Louisiana Purchase." Shaping of America, 1783-1815 Reference Library, edited by Lawrence W. Baker, et al., vol. 4: Primary Sources, UXL, 2006, pp. 137-145. Gale eBooks. "Louisiana Purchase." Gale Encyclopedia of U.S. Economic History, edited by Thomas Carson and Mary Bonk, vol. 2, Gale, 2000, pp. 586-588. Gale eBooks.