This film documents the exploration expedition led by Meriwether Lewis William Clark into the interior of North America in the early 19th century. We follow the Corps of Discovery as they winded their way across the unknown territory gained in the Louisana Purchase by the United States in their futile search for the legendary Northwest Passage. Along the way, they discovered wonderous new things as they depended on the aid of Native Americans like their adept guide, Sacagawea, as they conducted the most important exploration mission in American history.