The American explorer and soldier William Clark (1770-1838) was second in command of what has been called the American national epic of exploration, the Lewis and Clark expedition of 1804-1806, which traveled from the Missouri River to the Pacific Ocean.

William Clark was born on Aug. 1, 1770, in Caroline County, Va. He joined militia companies fighting local tribes in the Ohio country in 1789 and 3 years later won a lieutenant's commission in the U.S. infantry. He was on the Native American and Spanish frontier of the United States and served in Mad Anthony Wayne's successful campaign, terminated by the victory of Fallen Timbers (1794) over the Native Americans.

Clark resigned his commission in 1796, became a civilian, and tried to straighten out the chaotic financial condition of his famous brother, a hero of the Revolution, George Rogers Clark. However, when Meriwether Lewis offered him a role in what would be known...