What was the name of the 1804–1806 U.S. expedition that crossed North America to the Pacific Ocean?

The Lewis and Clark Expedition was the 1804–1806 U.S. expedition that crossed North America to the Pacific Ocean.

President Thomas Jefferson commissioned the expedition after the United States acquired the Louisiana Territory in 1803. Its official military name was the Corps of Discovery Expedition. Meriwether Lewis and William Clark led the main party, which included soldiers, civilian volunteers, and York, an enslaved man belonging to Clark.

The expedition departed from Camp Dubois in Illinois on May 14, 1804. It traveled up the Missouri River, crossed the Rocky Mountains, followed the Clearwater, Snake, and Columbia rivers, and reached the Pacific coast in late 1805. The group spent the winter at Fort Clatsop near present-day Astoria, Oregon.

The explorers returned to the United States in 1806 with maps, journals, scientific observations, and information about western geography and Indigenous nations. The expedition did not discover an all-water route across the continent, but it greatly expanded U.S. geographic knowledge after the Louisiana Purchase.