the first United States expedition to the Pacific Coast.
It was sent by President Thomas Jefferson and led by Meriwether Lewis and William Clark.
Their objects were both scientific and commercial - to study the area's plants, animal life, and geography, and to discover how the region could be exploited economically.
Jefferson placed special importance on declaring U.S. sovereignty over the Native American tribes along the Missouri River, and getting information about the resources in the recently-completed Louisiana Purchase.