A major consequence of the Louisiana Purchase in 1803 was the significant territorial expansion of the United States, doubling its size and opening vast lands for settlement. Acquired from France for $15 million, the purchase included land that would eventually become 15 states and provided opportunities for westward expansion, manifest destiny, and economic development. It also raised questions about the expansion of slavery into new territories, contributing to tensions that would later culminate in the Civil War. The Louisiana Purchase is considered a pivotal moment in U.S. history, setting the stage for the country's future growth and development.