Setting out from St Louis in May, 1804, the Lewis and Clark Expedition, under the leadership of Meriwether Lewis and William Clark, the expedition explored the new territory obtained for the United States by the Louisiana Purchase. It followed the Missouri River into what is now Montana, crossed the Rocky Mountains and followed the Snake River and Columbia River to the Pacific. After spending the winter of 1805-1806 near present-day Astoria, the expedition retraced its route, splitting into two groups before crossing the Rockies again and rejoining their forces in August 1806. They returned to St Louis in September, 1806.
Always considering science and geography as their principal objectives, the expedition returned with meticulous observations of the plants, animals, rivers, and people they met along the way.
