On October 20, 1803, the Senate ratified the Louisiana Purchase Treaty by a vote of twenty-four to seven. The agreement, which provided for the purchase of the western half of the Mississippi River basin from France at a price of $15 million, or approximately four cents per acre, doubled the size of the country and paved the way for westward expansion beyond the Mississippi.
Spain had controlled Louisiana and the strategic port of New Orleans with a relatively free hand since 1762. However, Spain signed the Treaty of San Ildefonso in 1800 under pressure from Napoleon Bonaparte, a secret agreement retroceding the territory of Louisiana to France.
News of the agreement eventually reached the U.S. government. President Thomas Jefferson feared that if Louisiana came under French control, American settlers living in the Mississippi River Valley would lose free access to the port of New Orleans. On April 18, 1802, Jefferson wrote a letter to Robert Livingston, the U.S. minister to France, warning that, “There is on the globe one single spot, the possessor of which is our natural and habitual enemy. It is New Orleans…”
Napoleon, faced with a shortage of cash, a recent military defeat in Santo Domingo (present-day Haiti), and the threat of a war with Great Britain, decided to cut his losses and abandon his plans for an empire in the New World. In 1803, he offered to sell the entire territory of Louisiana to the United States for $15 million.
Robert Livingston and James Monroe, whom Jefferson had sent to Paris earlier that year, had only been authorized to spend up to $10 million to purchase New Orleans and West Florida. Although the proposal for the entire territory exceeded their official instructions, they agreed to the deal. The Louisiana Purchase Treaty was dated April 30 and formally signed on May 2, 1803.
The bounds of the territory, which were not clearly delineated in the treaty, were assumed to include all the land between the Mississippi River and the Rocky Mountains, at that time known as the Stony Mountains. Just twelve days after the signing of the treaty, frontiersmen Meriwether Lewis and William Clark, younger brother of Revolutionary War officer George Rogers Clark, set out on an expedition to explore the newly acquired territory.
The purchase of the Louisiana Territory and the Lewis and Clark expedition marked the beginning of a century of conquest. As explorers, speculators, adventurers, and settlers pushed the territorial boundaries of the United States westward toward the Pacific coast, the notion of America as a nation always pushing toward new frontiers took hold in art, literature, folklore, and the national psyche.
- The Thomas Jefferson Papers, 1606 to 1827 consist of approximately 27,000 documents, the largest collection of original Jefferson documents in the world. Search this collection on the word Louisiana to retrieve over one hundred documents and letters.
- See the entry for the Louisiana Purchase Treaty in the Library’s Primary Documents in American History Research Guide series to learn more about this document.
- Search on Louisiana Territory in A Century of Lawmaking for a New Nation: U.S. Congressional Documents and Debates, 1774-1875 to read congressional acts and proceedings related to the vast territory. The special presentation The Louisiana Purchase: A Legislative Timeline – 1802 to 1807 explores the role of Congress in the Louisiana Purchase from 1802 to 1807, including ratification of the treaty, establishment of a territorial government, confrontation with Spain over boundary issues, and its limited role in the Lewis and Clark expedition.
- Louisiana: European Explorations and the Louisiana Purchase presents a rich variety of research materials including maps, letters, and newspapers, as well as a lengthy essay relating to that landmark event. Browse the collection by Subjects, Contributors, or Locations.
- France in America is a bilingual multi-format digital library project between the Library of Congress and the Bibliothèque nationale de France. Search on Louisiana purchase for information on the French presence in America and the interactions between the French and American peoples.
- See a map of Lewis and Clark’s track copied by Samuel Lewis from the original drawing of William Clark, or a Lewis and Clark map with annotations in brown ink by Meriwether Lewis in the Library’s Maps collections. Search these collections on Louisiana for maps of the territory and state. Find maps of the states, towns, and land features that were originally part of the Louisiana Territory by searching on their names.
- Read Henry Rowe Schoolcraft’s memoir of his 1832 discovery of the Mississippi River’s source, Lake Itasca, Minnesota, found in the collection Pioneering the Upper Midwest: Books from Michigan, Minnesota, and Wisconsin, ca. 1820 to 1910.
- The online exhibition Rivers, Edens, Empires: Lewis & Clark and the Revealing of America features the Library’s rich collections of exploration material documenting the quest to connect the East and the West by means of a waterway passage.
- The James Madison Papers, 1723 to 1859 consist of approximately 12,000 items, spanning the period 1723-1859. Search the Madison Papers to find papers related to the Louisiana Purchase, including a proposed amendment to the Constitution regarding Louisiana dated July 9, 1803.