In 1804, Lewis and Clark began the first exploration of the American west. They began their journey in St. Louis, and followed which river westward for 1,000 miles ?

The famed Corps of Discovery expedition, led by Meriwether Lewis and William Clark, used North America's longest river as its primary highway into the continent's interior. Setting out in May 1804 from their camp near St. Louis, the team navigated their large keelboat and smaller pirogues against the powerful current of the Missouri. This waterway served as their guide through the vast, uncharted territory of the recent Louisiana Purchase. For the first year and a half of their journey, the expedition painstakingly followed its winding path, covering well over 1,000 miles as they pushed toward its source in the Rocky Mountains.

President Thomas Jefferson had commissioned the expedition to find a water route to the Pacific, and the Missouri was seen as the key to this potential "Northwest Passage." As they traveled, Lewis and Clark were also tasked with mapping the new territory, establishing trade relations with dozens of Native American nations, and documenting the region's diverse plants and animals. The river was a challenging and often treacherous guide. The crew had to contend with strong currents, collapsing riverbanks, and submerged logs, often having to pull their heavy boats by rope from the shore. This arduous upriver journey represented the critical first leg of their epic trek to the Pacific Ocean and back.