In 1804, Leslie Edwards, a foppish aristocrat, and the loud, low-brow Bartholomew Hunt are competing against the renowned Lewis & Clark to be the first to chart and make it across the United States to the Pacific Ocean. In the beginning of the film, Edwards has high hopes to head the first expedition to make it across the U.S., but while he has ambition and funding, he has grown up sheltered and knows little of the wilderness he seeks to cross. To aid in his journey, he hires the services of a supposedly knowledgeable wilderness-man and tracker, Hunt, who, once they get underway, turns out to be less than advertised.

They are aided by a crew of varied, rugged and grizzled frontiersmen, including the group's version of Sacagawea, a young Indian woman by the name Shaquinna, who is integral in helping them find their way across the dangerous and unknown terrain ahead, as well as eventually becoming Edwards' love interest. Along the way, the group goes through various mishaps and ordeals from having to deal with quirky, indigenous Indian tribes and vicious eagles, to running out of food and romantic snafus, as Hunt's ineptness often causes more problems than it solves. Along the way, Edwards and Hunt's shared journey helps Edwards shed his aristocratic, snooty ways and he learns camaraderie and honor, as well as a more humble view of a world he thought he understood. Hunt finds true friendship in Edwards and a sense of self-confidence he had not known before.

After many hardships and setbacks, they eventually make it to the Pacific coast just minutes before Lewis and Clark's expedition; however, once the celebration is over, they find that they do not necessarily want to go back to their old lives and collectively decide to continue their adventure, leading Edwards and Hunt's expedition to further explore the great uncharted world.