Lewis & Clark Expedition Español In 1803 President Thomas Jefferson guided a splendid piece of foreign diplomacy through the U.S. Senate: the purchase of Louisiana territory from France. After the Louisiana Purchase Treaty was made, Jefferson initiated an exploration of the newly purchased land and the territory beyond the "great rock mountains" in the West. He chose Meriwether Lewis to lead an expedition, who in turn solicited the help of William Clark. Together they formed a diverse military C