The primary purpose of the Louisiana Purchase in 1803 was to acquire a vast territory from France, significantly expanding the United States. The U.S. aimed to secure land for agriculture and settlement, as well as control the Mississippi River, which was vital for trade. President Thomas Jefferson sought to double the size of the nation and ensure the availability of resources to support a burgeoning population. The purchase, involving roughly 828,000 square miles, cost $15 million and was a pivotal moment in U.S. history, facilitating westward expansion and shaping the nation's future development.