The Lewis and Clark expedition was an early exploration of the immense area, which is now known as the northwestern United States. This expedition was funded by the U.S. government and headed by U.S. Army Officers Meriwether Lewis and William Clark. This journey began near St. Louis, Missouri, in May 1804 and ended at the same place in September 1806.
The total amount of miles traveled on this expedition was about 8,000 miles (12,800 kilometers). They started near St. Louis at a camp and journeyed up the Missouri River, across the Rocky Mountains, and along the Columbia and other rivers to the Pacific coast. They then returned to St. Louis with information such as; maps of their route and the surrounding regions; specimens and descriptions of plant, animal, and mineral resources; and information about the native Indians of the west. The successful outcome of the expedition enabled the United States to claim the Oregon region, which included the now known states of Oregon, Washington, and Idaho. .
Not long after Thomas Jefferson became the President, in 1801, he started to organize an expedition to chart a route through the Louisiana Territory and Oregon Region. He had faith that a route to the Pacific Coast along the Missouri and Colombia Rivers may be part of a land-and-water passage in the middle of the Pacific and Atlantic Oceans. Jefferson's plan was to gather scientific information about the regions and establishing communication with the Indians that lived there. The United States purchased the Louisiana Territory from France in 1803, adding the extra task of tracing the boundaries of the Territory and laying United States claims to the Oregon Region.
Meriwether Lewis was chosen by President Jefferson to lead the expedition. Lewis was the President's private secretary and an U.S. Army Captain. Lewis chose a former U.S. Army officer named William Clark to join him. In order to join the expedition Clark re-enlisted in the Army in 1803, after resigning in 1796.