the first American expedition to cross the western portion of the continental United States. The journey started in May 1804 in St. Louis, Missouri and ended in September 1806 at the Pacific Ocean in present-day Oregon. Commissioned by President Thomas Jefferson, the expedition was led by Meriwether Lewis and William Clark, whose goal was to map the territory and find a practical route to the Pacific Ocean. The expedition is also known officially as the Corps of Discovery Expedition.
