The United States bought the Louisiana Purchase from France in 1803.
President Thomas Jefferson authorized negotiations to secure New Orleans and access to the Mississippi River. Instead, French representatives offered the United States the entire Louisiana territory, and American negotiators agreed to purchase it for $15 million.
The acquisition was formally dated April 30, 1803, and the United States took possession later that year. It transferred a vast region west of the Mississippi River from Napoleonic France to the United States, even though France’s control over parts of the territory had been limited.
The purchase nearly doubled the nominal size of the United States. It included land that later became all or part of 15 present-day U.S. states and two Canadian provinces. The expedition of Meriwether Lewis and William Clark soon explored the northern portion, beginning in 1804.