The Lewis and Clark Expedition, also known as the "Corps of Discovery Expedition" (1804–1806), is the first transcontinental expedition to the Pacific coast undertaken by the United States.

Commissioned by President Thomas Jefferson, it is led by two Virginia-born veterans of Indian wars in the Ohio Valley, Meriwether Lewis and William Clark.

Their objectives are both scientific and commercial – to study the area's plants, animal life, and geography, and to learn how the region can be exploited economically.