The United States completed the Louisiana Purchase in 1803, a major expansion remembered in the history celebrated by America250. The agreement with France transferred about 828,000 square miles of territory for $15 million.
President Thomas Jefferson authorized the purchase from Napoleon Bonaparte’s government. The territory stretched from the Mississippi River to the Rocky Mountains and from the Gulf of Mexico toward the Canadian border, although its exact boundaries were not immediately clear.
The United States and France signed the purchase treaty on April 30, 1803. The Senate ratified it later that year, and the formal transfer took place in New Orleans on December 20, 1803. The deal effectively doubled the size of the United States.
The purchase did not mean that every modern state in the region was immediately organized or settled by the United States. Much of the territory was explored by the Lewis and Clark Expedition, which began in 1804, and its lands were later divided into territories and states.