1752-1818

He defended the Northwest Territories - land lying north of the Ohio River, south of Canada, east of the Mississippi River, and west of Pennsylvania - against British attacks.

He captured key British settlements which enabled the United States to claim this land during peace negotiations with the British.

In 1783, Thomas Jefferson, then a member of Congress, asked Clark to explore the land west of the Mississippi. He declined the offer. In 1803, Jefferson asked Clark's brother, William Clark to explore this land and therefore William Clark became part of the Lewis and Clark Expedition.