The Louisiana Purchase, made in 1803, was significant for westward expansion in the U.S. as it doubled the nation's land area and provided vast territories for settlement and exploration. Acquiring approximately 828,000 square miles from France for $15 million, it allowed for further migration of settlers westward, fostering growth in agriculture and commerce. The purchase also eliminated French influence in North America. This expansion played a crucial role in shaping the nation's identity and paved the way for later conflicts over slavery in new territories, ultimately influencing the country's trajectory leading up to the Civil War.