The Lewis and Clark Expedition was a famous exploration of the western portion of North America by the United States. Meriwether Lewis and William Clark led the expedition from 1804 to 1806, exploring the Louisiana Purchase and beyond. Their goals were to find a practical route across the continent, study the native tribes they encountered, and claim the land for the United States before European countries could. The expedition covered around 8,000 miles in total over two years and helped map much of the western half of the current United States.