Which 1803 agreement doubled the territory of the United States?

The Louisiana Purchase doubled the territory of the United States in 1803.

The United States purchased the Louisiana Territory from France for $15 million. The agreement was signed on April 30, 1803, and the transfer was formally completed later that year. The territory covered about 828,000 square miles west of the Mississippi River, stretching from the Gulf of Mexico toward the Rocky Mountains.

President Thomas Jefferson supported the deal because control of the Mississippi River and the port of New Orleans was vital to western farmers and traders. The purchase also removed French power from a large part of North America, although the territory’s boundaries were not perfectly defined at first.

The acquisition expanded the young republic dramatically, but it also raised difficult questions about Indigenous sovereignty, slavery, and the political status of future states. Much of the land was surveyed during later expeditions, including the Lewis and Clark Expedition.