The United States agreed to pay France $15 million for the Louisiana Purchase in 1803.
The transaction transferred roughly 828,000 square miles of territory west of the Mississippi River to the United States. It more than doubled the country’s size and gave the United States control of the Mississippi River and the port of New Orleans.
President Thomas Jefferson authorized negotiations with France after becoming concerned about American access to New Orleans. Napoleon Bonaparte, facing renewed war with Britain and the failure of French plans in the Caribbean, decided to sell the entire Louisiana Territory rather than retain a vulnerable North American empire.
The $15 million figure is sometimes described simply as the purchase price, though the United States also agreed to assume certain French debts owed to American citizens. The deal was finalized in 1803 and ratified later that year.