The United States paid 15 million dollars for the Louisiana Purchase in 1803.
The deal transferred the Louisiana Territory from France to the United States. The agreement was signed in Paris on April 30, 1803, by Robert Livingston, James Monroe, and François Barbé-Marbois. The territory stretched across much of the Mississippi River basin and included land that later became all or parts of numerous states.
President Thomas Jefferson had initially instructed American diplomats to seek New Orleans and nearby territory. Napoleon Bonaparte's decision to abandon plans for a French North American empire created an opportunity for a much larger purchase. The final territory nearly doubled the area of the United States.
The $15 million figure is often remembered as a simple cash price, but the transaction involved government bonds and an assumption of certain French debts owed to American citizens. The purchase also raised constitutional questions because the Constitution did not explicitly describe acquiring foreign territory, yet Congress approved the treaty and related measures.