Lewis & Clark Expedition started from August 31, 1803 to September 15, 1806, it can also be known as “Corps of Discovery Expedition”. It was an expedition in the U.S. trying to cross the western part of the country after the Louisiana Purchase had happened. Thomas Jefferson had actually commissioned them after the Louisiana Purchase, to explore the lands and map out the areas, while also trying to find an easy route to the western half of the continent.