What 1803 land deal added about 828,000 square miles to the United States?

The Louisiana Purchase added about 828,000 square miles to the United States in 1803.

The United States purchased the territory from France for $15 million. President Thomas Jefferson authorized the deal, which more than doubled the country’s size and transferred control of the Mississippi River and the port of New Orleans to the United States.

The territory extended west from the Mississippi River toward the Rocky Mountains and included land that later became all or part of numerous states. The transaction was finalized through treaties signed in Paris on April 30, 1803, and the United States formally took possession later that year.

A common misunderstanding is that the purchase represented fully controlled and unoccupied land. Much of the territory was inhabited by Native American nations, and France’s claim did not mean France administered every part of it. The acquisition nevertheless transformed the young republic and led to exploration, settlement, diplomacy, conflict, and major debates over slavery’s expansion.