What was the 1803 U.S. acquisition of French territory west of the Mississippi River called?

The 1803 U.S. acquisition of French territory west of the Mississippi River was called the Louisiana Purchase.

The United States agreed to purchase the territory from France in 1803 for $15 million. The land covered approximately 828,000 square miles and stretched from the Mississippi River to the Rocky Mountains, although its western and northern boundaries were not precisely understood at the time.

President Thomas Jefferson supported the purchase because control of New Orleans and the Mississippi River was vital to western farmers and merchants. The deal nearly doubled the area of the United States and opened a vast region to later exploration, settlement, and territorial organization.

The purchase did not immediately create new states. Congress organized portions of the acquired land into territories, and the Lewis and Clark Expedition began in 1804 to survey and describe the region. The Louisiana Purchase is distinct from the later Gadsden Purchase, which involved a much smaller area acquired from Mexico in 1854.