The land acquisition made by the U.S. in 1803 known as the "Louisiana Purchase" involved the acquisition of approximately 827,000 square miles of territory from France. The purchase, negotiated by President Thomas Jefferson, effectively doubled the size of the United States and opened vast tracts of land for exploration and settlement. It included parts of 15 modern states and gave the U.S. control over the Mississippi River, crucial for trade and transportation. The Louisiana Purchase is often seen as a pivotal moment in American history, significantly shaping the nation's expansion westward and its emergence as a continental power.