The Lewis and Clark Expedition (1804–1806), commissioned by President Thomas Jefferson, explored the Pacific Coast and the western United States.

Led by Meriwether Lewis and William Clark, the expedition's goal was to map the newly acquired Louisiana Territory, find a practical route to the Pacific Ocean, and establish an American presence in the uncharted west before European powers could claim it. The team reached the Pacific Coast at the mouth of the Columbia River in present-day Oregon in 1805. Their journey provided valuable geographic, cultural, and scientific information about the region, including detailed maps and observations about the land, wildlife, and Native American tribes they encountered.