The Lewis and Clark Expedition is credited with mapping the western coastline of North America during the early 1800s. Commissioned by President Thomas Jefferson after the Louisiana Purchase in 1803, the expedition aimed to explore the newly acquired territory and establish a route to the Pacific Ocean. Led by Meriwether Lewis and William Clark, the journey provided invaluable geographic and scientific information about the region, fostering U.S. expansion and settlement. Their findings significantly impacted relations with Native American tribes and laid the groundwork for future exploration.