Steamboat inventor Robert Fulton shows up in New York in 1807. Tavern keeper (Faye) believes in him, but her boyfriend (MacMurray) doesn't. All seems lost when sailors afraid of losing their jobs burn his boat.

In New York in 1807, the courtly Robert Fulton, newly arrived from England and proudly bearing his model for a revolutionary new steam boat, stops at a waterfront tavern owned by the blustery yet fanciful Pat O'Day. There, Robert is assaulted by Regan, a bullying ship yard owner, and when Regan's employee, Charles Brownne, refuses to join the brawl, Regan fires him. After licking Regan, Robert hires Charlie to build the hull for his new boat. When his financial backer, Robert Livingstone, withdraws his funding, Robert is about to give up his dream until Livingstone's niece Harriet, who is in love with Robert, convinces her uncle to refinance the boat. As the boat nears completion, Regan incites his men to destroy the vessel. Undaunted, Harriet and Pat, who is also in love with Robert, set about raising money for a new hull. Another obstacle in Robert's path appears when Jefferson's embargo threatens delivery of his engine, but under cover of fog, Robert and his men steal the engine from the embargoed ship's hold. More problems arise when Pat's feelings for Robert cause friction between him and Charlie, but Robert ends the rivalry by declaring his love for Harriet. With all impediments removed, Robert's ship, the Clermont , begins to navigate under its own steam, astounding skeptics and revolutionizing river travel.