William Clark (August 1, 1770 – September 1, 1838) was an American explorer, soldier, Indian agent, and territorial governor. A native of Virginia, he grew up in pre-statehood Kentucky before later settling in what became the state of Missouri.
Along with Meriwether Lewis, Clark led the Lewis and Clark Expedition of 1804–1806 across the Louisiana Purchase to the Pacific Ocean, the first major effort to explore and map much of what is now the Western United States and to assert American claims to the Pacific Northwest. Before the expedition, he served in a militia and the United States Army. Afterward, he served in a militia and as governor of the Missouri Territory. From 1822 until his death in 1838, he served as a U.S. Superintendent of Indian Affairs in St. Louis.