The Show Boat's in town! But its star Julie LaVerne is in trouble when it's discovered she's mixed race and married to a fellow performer who's white. They are forced to leave the show and run out of town by the sherrif for breaking the law by 'race mixing'. Magnolia, the naive daughter of the Captain is thrust into the limelight as the show's new star.

A rich portrait of changing American entertainment traditions and race relations spanning five decades, the film also features the magical rendition of Ol' Man River from Paul Robeson. The film is notable for content which would have been controversial at the time it was made, subjects such as single-motherhood, desertion, gambling and 'race' mixing shows the film's progressive approach to taboo subjects. 

This film inevitably has historical depictions and language which modern audiences find difficult to watch, including stereotypical black characters and one number in blackface. However, the film is notable for its frank portrayal of race and critiques race relations at the time, as well as featuring central performances from African-American actors.