In 1803, Meriwether Lewis (MacMurray) and William Clark (Heston), with President Thomas Jeffersons blessing, embarked on the government-sponsored Lewis & Clark Expedition an attempt to discover a water route connecting St. Louis, Missouri, with the Pacific Ocean. Their trek takes them through the magnificent, danger-filled territory of the Pacific Northwest, with guidance from the Native American maiden Sacajawea (Reed). Its an adventurous journey into country that, at the time, had yet to be seen by anyone except native tribes.