William Clark was born into a prominent Virginia plantation family and was the youngest brother of George Rogers Clark, hero of western operations in the War of Independence.
As a young man, Clark fought in wars against Native Americans in the West, seeing action in the Battle of Fallen Timbers. He became acquainted with Meriwether Lewis during those campaigns, and with whom he shared command of the Lewis and Clark Expedition (1804-06).
Clark capitalized on his fame as an explorer and served as governor of the Missouri Territory from 1813 to 1821, then as the Superintendent of Indian Affairs in St. Louis from 1822 until his death in 1838.