Andy Hawks, Captain of the show boat Cotton Blossom
Parthenia Ann (“Parthy”) Hawks, his wife
Magnolia Hawks, their 18-year-old daughter
Gaylord Ravenal, a riverboat gambler
Joe, a crewmember on the Cotton Blossom
Queenie, Joe’s wife and the ship’s cook
Julie La Verne, the acting troupe’s leading lady
Steve Baker, the troupe’s leading man and Julie’s husband
1887: After the Cotton Blossom docks in Natchez, a fight over Julie La Verne breaks out between her husband Steve and the boat’s engineer Pete. Pete claims he knows an important secret about Julie’s past. Cap’n Andy tells the assembled crowd that the fight is part of a melodrama his troupe will perform. Gaylord Ravenal appears; he is immediately attracted to Magnolia Hawks and she to him. Magnolia confesses her newfound love to Julie, who cautions her that Ravenal may be a “no-account river fellow.” Magnolia says that she would stop loving him if that were true; Julie replies that it’s not so easy to do so, singing “Can’t Help Lovin’ That Man.” Queenie is surprised, saying she has only heard “colored folks” sing that song before.
The town sheriff arrives, intending to arrest Julie and Steve. Pete has disclosed that Julie is of mixed-race parentage; her marriage to a white man violates local laws against miscegenation. Thanks to a clever ruse, Steve is also able to claim having a mixed-race background, which forestalls their arrest but forces them to leave the show boat, because they will no longer be acceptable to white audiences as the romantic leads.
Ravenal returns and Cap’n Andy hires him as the new leading man, partnering him with Magnolia as Julie’s replacement. Their rehearsal of love scenes becomes increasingly realistic, annoying Parthy, Magnolia’s mother. Ravenal and Magnolia are soon onstage hits and offstage fiancées. They wed, despite Parthy’s objections.
1893: Gaylord and Magnolia are in Chicago, living luxuriously at the Palmer House off the former’s gambling winnings.
1903: Now down on their luck, Gaylord and Magnolia having been living in a boarding house with their young daughter, Kim. Frank and Ellie, two performers from the Cotton Blossom, chance upon Magnolia, who has been abandoned by Ravenal. They arrange an audition for Magnolia at the Trocadero, where they and Julie La Verne have been performing. When she hears Magnolia auditioning, Julie secretly quits her job so that Magnolia will be hired.
New Year’s Eve: Cap’n Andy and Parthy make a surprise visit to Chicago, but cannot find Magnolia at the Palmer House. Andy discovers her at the Trocadero, where his presence boosts her failing confidence. Her show-stopping performance leads her to become an internationally known musical comedy star.
1927: The Cotton Blossom is again docked at the Natchez levee, where Kim performs. Magnolia has retired from the stage and her return to the show boat gives Cap’n Andy the opportunity to steer a reconciliation between Gaylord and Magnolia.