The Louisiana Purchase

Encompassing the western half of the Mississippi River basin, the Louisiana Territory was acquired from France in 1803. At less than three cents per acre for 828,000 square miles (2,144,520 square km), it was the greatest land bargain in U.S. history. The purchase doubled the size of the United States, greatly strengthened the country materially and strategically, provided a powerful impetus to westward expansion and confirmed the doctrine of implied powers of the federal Constitution.