The total purchase price in 1803 for the Louisiana territory acquired by the United States was $15 million.
The agreement transferred an enormous region from France to the United States and added about 828,000 square miles of territory. The payment worked out to approximately $18 per square mile, although the territory's boundaries and the exact extent of French control were subjects of later interpretation.
France had regained Louisiana from Spain in 1800, but Napoleon soon reconsidered the value of maintaining a North American empire. War with Britain and the loss of French influence in Saint-Domingue encouraged the sale. President Thomas Jefferson's administration completed the deal in 1803.
The purchase did not mean the land was empty or unclaimed. Numerous Indigenous nations lived across the region, and the United States later pursued treaties, settlement, and military expansion there. It is also distinct from the 1867 Alaska Purchase, which cost $7.2 million.