Which regions did Lewis and Clark explore?

Two US Army officers, Meriwether Lewis and William Clark, traveled from 1804 to 1806 across North America to draw map. They left St. Louis, went down the Missouri River, and crossed the Rockies. Then they explored the west of the Columbia River to the Pacific, before returning to the east. Lewis and Clark mapped many tracts in the West, showing the way for future travelers from California and other western territories.