The Louisiana Purchase, completed in 1803, had a profound impact on American territory, effectively doubling the size of the United States. The U.S. acquired approximately 828,000 square miles of land from France, which included parts of 15 current states and provided vast natural resources, fertile land, and opportunities for westward expansion. This acquisition laid the foundation for the nation's future growth and development, fostering a sense of Manifest Destiny and solidifying the U.S. as an emerging power. It also intensified debates over slavery and governance in the newly acquired territories, shaping political discourse and conflicts in the years leading up to the Civil War.