The Kingdom of France had controlled the Louisiana territory from 1682 until it was ceded to Spain in 1762. In 1800, Napoleon, the First Consul of the French Republic, regained ownership of Louisiana in exchange for Tuscany as part of a broader effort to re-establish a French colonial empire in North America. However, France's failure to suppress a revolt in Saint-Domingue, coupled with the prospect of renewed warfare with the United Kingdom, prompted Napoleon to consider selling Louisiana to the United States. Acquisition of Louisiana was a long-term goal of President Thomas Jefferson, who was especially eager to gain control of the crucial Mississippi River port of New Orleans. Jefferson tasked James Monroe and Robert R. Livingston with purchasing New Orleans. Negotiating with French Treasury Minister François Barbé-Marbois, the U.S. representatives quickly agreed to purchase the entire territory of Louisiana after it was offered.

Source: Wikipedia