Napoleon Bonaparte needed to raise funds after a disastrous campaign on the island of Hispanola, not far from the modern-day state of Louisiana. President Thomas Jefferson needed new lands to continue his new country’s expansion westward. Negotiating for a small part of the Mississippi territories, he had no idea that the Emperor would about make him the offer of a lifetime.

On this day, March 10, in 1804, Jefferson and Napoleon completed the Louisiana Purchase. Some 800,000 miles of land, from the gulf coast to the Rocky Mountains, were transferred to the control of the United States, just about doubling the country’s size. The asking price was 60 million francs, equivalent to about 15 million dollars.

Interestingly, Jefferson’s agreement was technically in violation of the Constitution. The federal government was not empowered to acquire lands by treaties. Jefferson ventured that the opportunity to acquire such an enormous tract of land far outweighed the risks of impeachment, and in November of that year the House of Representatives passed an act authorizing the payment and treaty.