France had controlled the Louisiana Territory from 1699 until 1762, when it ceded the territory to Spain as part of the French and Indian War. Before it relinquished the territory, France controlled more of the territory that is now the United States than any other European power. When Spain controlled the territory, it did not develop its new lands. In 1800, Spain, France's ally, gave the territory to France as part of a covert treaty, as Napoleon sought to reestablish France's presence in North America.

However, by 1803, Napoleon offered the United States under Jefferson the opportunity to purchase the Louisiana Territory. Napoleon was having financial difficulties, and France had also failed to put down a revolution in its colony of Saint-Domingue (now Haiti). In addition, Napoleon anticipated a war with Great Britain and had to deal with the British naval blockade of France. In 1803, the US purchased the territory, doubling the size of the country.

Napoleon acquired the Louisiana Territory from the Spanish Empire because he hoped to revive New France--the French colonies in the Western hemisphere. Some historians speculate that Napoleon also acquired Louisiana to prevent the United States from growing any larger. However, there were several reasons he changed his mind and decided to sell Louisiana to the United States.

First, he needed money for an impending war with Great Britain. Second, a recent slave revolt in a French colony in Haiti demonstrated the difficulty of managing New World colonies from Europe. Third, the Americans were prepared to go to war with France to retain the ability to ship cargo through New Orleans (New Orleans was an important connection between the Gulf of Mexico and the Mississippi River). For these reasons, Napoleon decided he was better off selling Louisiana to the United States and using the profits to finance his empire in Europe.