The Louisiana Purchase nearly doubled the territory of the United States in 1803, making it a major expansion in the historical story surrounding America250.
The United States acquired the territory from France for $15 million. The agreement covered about 827,000 square miles west of the Mississippi River, although the exact boundaries were initially uncertain. President Thomas Jefferson authorized the purchase, and the Senate ratified the treaty in October 1803.
The purchase extended from the Mississippi River toward the Rocky Mountains and included land that later became all or part of fifteen states. It did not immediately create those states, and much of the region remained under Indigenous control and sovereignty. The Lewis and Clark Expedition was launched partly to explore the new territory and find a practical route to the Pacific.