The Louisiana Purchase took place in 1803.
The United States acquired the Louisiana Territory from France during President Thomas Jefferson's administration. The agreement was signed on April 30, 1803, and the United States formally took possession later that year. The purchase covered about 828,000 square miles west of the Mississippi River.
The deal more than doubled the size of the United States and gave the nation control of the Mississippi River and the port of New Orleans. The United States paid France $15 million, including the assumption of certain claims by American citizens against France.
A common mix-up is confusing the Louisiana Purchase with the later annexation of Texas or the Mexican Cession. The purchase was negotiated with France, whose leader Napoleon Bonaparte had decided to sell the territory after abandoning plans for a French empire in North America.