The massive migration and the subsequent rapid settlement of the continental USA were fueled by the Gold Rush, the Oregon Trail (large-wheeled wagon road and emigrant trail in the United States that combined the Missouri River to valleys in Oregon) and a belief in "manifest destiny", the idea that its settlers were designed to expand across North America. This expansion began with the Louisiana Purchase in 1803. The president Thomas Jefferson bought the territory from the French for $15 million, and worked in the creation of an expansionist mentality. As a result this migration is also called Westward Expansion.
