He co-led an 1804 expedition to explore the Pacific Northwest
In 1804 they ascended the Missouri River to the Mandan Indian villages near
... [DOC] [TLE] Corps of Discovery - The Lewis & Clark Expedition [PAR] The Lewis and Clark expedition (1804-1806) was the first United States ... to 
send a small U.S. Army unit to explore the west all the way to the Pacific Ocean.