In 1804 Merriwether Lewis and William Clark departed from Camp Wood in what is today Illinois. President Jefferson requested that Congress fund this expedition to the unexplored west shortly before the Louisiana Purchase. Lewis and Clark were ordered to document all they saw with detailed maps. Lewis and Clark and 45 others traveled for three years through lands that would later become 11 separate states. Most of the trail they took follows the Missouri and Columbia rivers. This trail is the second longest of the National Historic and Scenic trails and totals 3,700 miles. Much of the trail still remains intact today and it is possible to follow some of it by automobile or by hiking and biking. Segments run through the Upper Missouri River Breaks National Monument. Congress established the Lewis and Clark trail in 1978.