Which U.S. president authorized the Louisiana Purchase in 1803?

Thomas Jefferson authorized the Louisiana Purchase in 1803.

Jefferson instructed James Monroe and Robert R. Livingston to negotiate with France for New Orleans and nearby territory. Instead, Napoleon Bonaparte’s government offered to sell the entire Louisiana Territory. The negotiators accepted, and the treaty was signed on April 30, 1803, for $15 million.

The acquisition nearly doubled the size of the United States and secured control of the Mississippi River and the port of New Orleans. The territory covered land that later became parts of many states, including Louisiana, Missouri, Arkansas, Iowa, and Kansas. Jefferson then supported congressional funding and ratification despite concerns about whether the Constitution explicitly authorized such a purchase.

The United States announced the agreement on July 4, 1803. The Lewis and Clark Expedition began in 1804 to explore and map the new territory. A common confusion is to credit Monroe as president; he was a negotiator and later became president, while Jefferson authorized the purchase.