In 1804, Lewis and Clark are commissioned by President Thomas Jefferson to explore the newly acquired Louisiana Purchase. They have a number of men and a dog to help them. Along the way, they meet Sacagawea who knows the territory and speaks a number of tribal languages. They amaze Indians with airgun demonstrations and other technological innovations. With tales of the Great White Father, gold commemorative medals, and a host of trinkets, they persuade various tribal leaders to sign oaths of allegiance to the United States. Trekking across the United States, the expedition eventually makes it to the Pacific Ocean.