Which expedition explored the Louisiana Purchase and reached the Pacific Ocean from 1804 to 1806?

The Lewis and Clark Expedition explored the Louisiana Purchase and reached the Pacific Ocean from 1804 to 1806.

President Thomas Jefferson commissioned Meriwether Lewis and William Clark to lead the Corps of Discovery after the United States acquired the Louisiana Purchase from France in 1803. The expedition departed near St. Louis in May 1804 and traveled up the Missouri River, across the Rocky Mountains, and down the Columbia River.

The party reached the Pacific coast in November 1805 and returned to St. Louis in September 1806. Its members mapped routes, recorded plants and animals, and documented many Indigenous nations and communities. Sacagawea, a Lemhi Shoshone woman, accompanied the expedition with her infant son and helped with communication and travel.

The expedition did not discover an unknown continent; Indigenous peoples had long lived throughout the region, and European exploration had preceded it in parts of the West. Its importance was that it provided the young United States with extensive information about its newly acquired western lands.