The Lewis and Clark Expedition, commissioned by President Thomas Jefferson in 1804, aimed to explore the newly acquired Louisiana Territory and find a route to the Pacific Ocean. Led by Meriwether Lewis and William Clark, the expedition provided valuable information about the geography, biology, and indigenous peoples of the American West. Their journey lasted until 1806, covering over 8,000 miles. It resulted in detailed maps and strengthened the U.S. claim to the Pacific Northwest, paving the way for westward expansion.