What was the cost of the Louisiana Purchase from France in 1803?

The 1803 purchase from France of 828,000 square miles of land, stretching from the Mississippi River to the Rocky Mountains, now known as Louisiana, cost $15 million.

This put the price of each acre of land at about 3 cents.

The purchase of Alaska from Russia in 1867 cost $7.2 million.

This made the selling price of each acre about 2 cents.