Frontier and Indian fighter who won fame as an explorer by sharing with Meriwether Lewis leadership of the epic expedition to the Pacific Northwest (1804-06); he later played an essential role in the development of the Missouri Territory.

William removed in 1784 with his father and mother to the falls of the Ohio, taking up their residence on the tract located by George Rogers Clark, where in 1777 he had built a fort. Here the settlers were constantly harassed by the Indians and the boy grew up an adept in Indian warfare. William entered military service in 1789 and marched with Col. John Hardin against the Indians across the Ohio in that year. William was appointed an ensign in 1791; served under Scott and Wilkinson against the Indians on the Wabash and was commissioned a first lieutenant in the fourth sub-legion by President Washington in March 1793. He served under General Wayne, conducted an expedition up the Wabash to Vincennes; returned to Fort Washington (Cincinnati) in the spring of 1794; escorted with a few men valuable trains of supplies and defended them against the Indians, receiving from General Wayne thanks for his good conduct. In July, 1796, continued ill-health compelled him to resign from the army and he resided at the falls of the Ohio for nearly eight years.

On the heels of the U. S. purchase of the Louisiana Territory (1803), Captain Clark welcomed an invitation from Captain Lewis to share the leadership in an extensive exploration of the vast unchartered area of the Northwest. The Lewis and Clark Expedition thus embarked on a three-year trek from the St. Louis area overland to the Pacific Ocean and back—an enterprise that succeeded largely because of the harmonious and complementary leadership provided by the two men. Proving particularly daring and resourceful, Clark—who had considerable frontier experience—was credited with rescuing the expedition from disaster on more than one occasion. He also served as map maker and artist, portraying with meticulous detail animal life observed en route.

The journals kept by Clark and other members of the group provided the nation with its first comprehensive description of this vast region.

Following the journey, President Thomas Jefferson awarded Clark 1,600 acres of public land and made him brigadier general of militia for the Louisiana (later Missouri) Territory as well as superintendent of Indian affairs operating out of St. Louis.

He visited the national capital upon his return; was commissioned 1st lieutenant in January, 1806, and was nominated lieutenant-colonel of the 2nd infantry, but his appointment failed of confirmation in the senate. He was appointed Indian agent at St. Louis in 1807, and was commissioned by congress brigadier-general for Louisiana Territory. In 1812 he declined a commission as brigadier-general with command of the army of the northwest as successor to General Hull. In 1813 he was made governor of Louisiana Territory, and upon the organization of the state of Missouri, in 1820, was the defeated candidate for its first governor.

In 1822 President Monroe made him superintendent of Indian affairs. He held this post the rest of his life, serving concurrently with his office as governor of the Missouri Territory, and Arkansas (1824-25). Throughout his long tenure in St. Louis, Clark continued to show an intense concern for Indian affairs and welcomed Indians into his home; he appealed many times to the federal government to show justice and humanity to the country’s first inhabitants.