On October 20, 1803, the United States Senate approved a treaty with France that provided for what is well-known as the Louisiana Purchase. This treaty permitted the U.S. to purchase the territory of Louisiana, which would in and of itself double the size of the United States. Although initially owned by Spain, the territory was now under the rule of Napoleon of France.

At that point in time, President Thomas Jefferson recognized the importance of obtaining and maintaining control of the Mississippi River. In 1803, President Jefferson sent James Monroe to France to speak with the French foreign minister about purchasing the territory. The goal was to convince Napoleon to sell West Florida and New Orleans to the United States. Shortly after James Monroe made the trek across the ocean, Napoleon was overcome with war with Great Britain. Because of this drastic change in events, Napoleon decided to offer the territory to the United States for a truly small sum of fifteen million dollars. In turn, he intended to use the money from this sale to fund his war and deny Great Britain the opportunity to overtake the territory in the U.S. and expand their forces even further. James Monroe was stunned by such an offer, and despite the fact that he lacked the true power to accept it, that’s exactly what he did.

After accepting Napoleon’s offer, James Monroe returned to President Thomas Jefferson in the United States. The President’s initial reaction was that the U.S. Constitution did not provide for the addition of territory by a treaty, and thus he questioned the constitutionality of the contract formed between Monroe and Napoleon. Despite his concerns, Jefferson ultimately sent the treaty on its way to be ratified. Upon review by the U.S. Senate, the treaty was ratified, and the Louisiana Purchase has since gone down in history as President Thomas Jefferson’s greatest achievement.