Meriwether Lewis (1774-1809), American explorer who served as co-leader, with William Clark, of the Lewis and Clark Expedition (1804-1806), the first American overland exploration of the West and Pacific Northwest. Born in Albemarle County, outside Charlottesville, Virginia, Lewis grew up in Virginia and Georgia as part of the Southern planter aristocracy. During his education, Lewis showed special talent for natural history, which encompassed the modern fields of botany and zoology. Lewis proved to be a keen observer of the natural world, an attribute he put to use during the expedition.
Lewis joined the Virginia militia as a private soldier during the Whiskey Rebellion, a series of disturbances in 1794 aimed against the imposition of a federal excise tax on whiskey. Lewis soon became a junior officer, and he transferred to the regular army in 1795. As an officer in the First Infantry Regiment, Lewis served in the Indian wars of the Ohio Valley, where he briefly spent time in the rifle company of William Clark, the eventual co-leader of the Lewis and Clark Expedition.
Meriwether Lewis's life changed dramatically in 1801, when President Thomas Jefferson selected the young officer as his personal secretary. At first Lewis's secretarial duties were routine and administrative. But those responsibilities suddenly grew larger once Jefferson decided to send an expedition to the Pacific. By the end of December 1802 Lewis was preparing a preliminary estimate of travel expenses for the journey, and he began to purchase supplies and consult with scientists in the spring of 1803.
By June 1803, as Jefferson drafted formal expedition instructions for Lewis, it became clear that the expedition was going to be larger and more complex than originally planned. Jefferson and Lewis agreed that the party needed a co-leader. Lewis turned to William Clark. By early December 1803 the expedition party, now known as the Corps of Discovery, assembled at Wood River camp outside St. Louis. Lewis, commissioned a captain, and Clark, commissioned a lieutenant, divided their time during the winter of 1803 to 1804 between training duties and visits to St. Louis.
During the expedition to the Pacific and back, Lewis and Clark worked out an informal but effective division of responsibilities. Lewis served as the expedition's naturalist, making detailed notes about plants and animals new to European and United States science. He also represented Jefferson's aspirations for an expanding American empire in the West. It was this role that led to Lewis's involvement in the expedition's only violent encounter with Native Americans. In late July 1806, on the expedition's return journey, Lewis led a small exploring party into present-day north central Montana. While looking for the northern reaches of the Marias River and an American claim to fur-rich country, Lewis came upon a group of Piegan Blackfoot warriors. When the young Piegans attempted to take Lewis's horses and guns, violence erupted and two Native Americans were killed.
When the expedition returned to St. Louis in September 1806, Lewis and Clark became national heroes. President Jefferson appointed Lewis governor of the Louisiana Territory, an administrative post for which the explorer was ill-suited. In the years that followed, Lewis struggled with one complex political problem after another. He also worked on a formal report of the expedition, making little progress. Lewis's temperament during this period was marked by episodes of depression. Personal financial difficulties, political troubles, questions about his effectiveness as governor, and the long-delayed expedition report all weighed heavily on him. In September 1809 Lewis left St. Louis for Washington, D.C., to answer his critics. Sometime during the night of October 10 near Hohenwald, Tennessee, Lewis apparently took his own life. Despite claims by some that Lewis was murdered, all the surviving evidence points to suicide. Lewis left behind a remarkable legacy of knowledge about the American West. Clark and American diplomat and financier Nicholas Biddle eventually published an abridged, two-volume collection of the expedition's journals in 1814. A complete set of the journals was finally published in 1905.