The Pike Expedition was a military party sent out by President Thomas Jefferson and authorized by the United States government to explore the south and west of the recent Louisiana Purchase. It was led by United States Army Lieutenant Zebulon Pike, Jr. who was promoted to captain during the trip. It was the first official American effort to explore the western Great Plains and the Rocky Mountains in present-day Colorado. Pike contacted several Native American tribes during his travels and informed them that the U.S. now claimed their territory. The expedition documented the United States' discovery of Tava which was later renamed Pikes Peak in honor of Pike.