The Louisiana Purchase was a massive land deal in 1803 that doubled the size of the United States. France sold approximately 828,000 square miles of land west of the Mississippi River to the United States for $15 million, working out to about 4 cents per acre. This land encompassed 15 current U.S. states and two Canadian provinces. The purchase provided the U.S. with critical access to the Mississippi River and Gulf of Mexico while removing an imperial presence along its borders.