The Louisiana Purchase more than doubled U.S. territory in 1803 during the 250-year story celebrated by America250.
The United States bought the Louisiana Territory from France for $15 million. The agreement was signed on April 30, 1803, and the transfer was completed later that year. The territory covered about 828,000 square miles, stretching west from the Mississippi River to the Rocky Mountains.
President Thomas Jefferson supported the purchase because control of the Mississippi River and New Orleans was vital to western farmers and trade. The deal also removed France from a major position in North America. Its enormous size opened opportunities for expansion while creating serious conflicts over Indigenous sovereignty, slavery, and the political balance between free and slave states.
The purchase is often confused with the Alaska Purchase, which transferred Alaska from Russia in 1867. The Gadsden Purchase was a much smaller acquisition from Mexico in 1853. Neither of those transactions had the same scale as the Louisiana Purchase.