CLARK, WILLIAM (177o-1838), American soldier and explorer, the youngest brother of George Rogers Clark, was born in Caroline county, Va., but early removed to Kentucky. He entered the U.S. army as lieutenant of infantry in 1 i92, and served under Gen. Anthony Wayne against the Indians in 1794. In 1803 06, with Meriwether Lewis, he commanded the famous exploring expedition from St. Louis to the mouth of the Columbia river and return, the first expedition to cross the continent within the limits of the United States. He was territorial governor of Mis souri from 1813 to 18 2o, and superintendent of Indian affairs at St. Louis from 1822 until his death in 1838.
See the Original Journals of the Lewis and Clark Expedition (1905), edited by R. G. Thwaites, the best of several editions of the leader's journals; George Bird Grinnell, Trails of the Pathfinders (191 I) ; "William Clark's Journal of General Wayne's Campaign, Mississippi Valley Hist. Rev., vol. i. p. (Cedar Rapids, Iowa, 1914) ; and Floyd Duckworth Welch, The Work of the Indian Agents in the Louisiana Purchase, (St. Louis, Mo., 1926).