It's believed that the failure of France to put down a slave revolution in Haiti, the impending war with Great Britain and probable British naval blockade of France – combined with French economic difficulties – may have prompted Napoleon to offer Louisiana for sale to the United States.
The completion of the Erie Canal spurred the first great westward movement of American settlers, gave access to the rich land and resources west of the Appalachians and made New York the preeminent commercial city in the United States.
The Trials and Successes of the Erie Canal. With the Louisiana Purchase, the United States doubled in size. This huge land deal also doubled the American people's desire for exploration and commerce. By the beginning of the 19th Century, the U.S. included much more than the original 13 Colonies.