France sold the Louisiana Purchase to the United States in 1803.
The agreement transferred a vast territory west of the Mississippi River to the United States during Thomas Jefferson’s presidency. The American negotiators, James Monroe and Robert R. Livingston, had initially been sent to seek New Orleans and its valuable port. French representatives instead offered the entire Louisiana territory, and the negotiators accepted.
The purchase nearly doubled the nominal size of the United States and gave the country control of the Mississippi River and New Orleans. It covered land that later became part of 15 present-day U.S. states and two Canadian provinces, although the exact borders were clarified through later agreements with Spain and Britain.
France had regained Louisiana from Spain in 1800 through the secret Treaty of San Ildefonso, but Napoleon Bonaparte’s plans in North America changed after the Haitian Revolution and renewed war with Britain. The United States paid $15 million, commonly described as about three cents per acre.