In 1917, in the Storyville district of New Orleans, Louisiana, Louis "Satchmo" Armstrong plays ragtime music with his band in the basement of the Orpheum cabaret. The cabaret, which also operates as a casino, is owned by Nick Duquesne, the "King of Basin Street." One of Nick's patrons, a wealthy widow named Mrs. Rutledge Smith, from Baltimore, Maryland, is joined in New Orleans by her daughter Miralee, a classically trained singer. Miralee's black maid, Endie, who is Satchmo's girl friend, introduces Miralee to the blues, and takes her to a "jam" session featuring Satchmo and his band. Nick discourages Miralee's love of ragtime because high society considers it immoral, and orders Grace Voiselle, a debutante, who is in love with Nick, to take her home. Jealous of Nick's attention toward Miralee, Grace calls Mrs. Smith and warns her to keep Miralee away from Nick. Mrs. Smith, who earlier had lost ten thousand dollars at the Orpheum, wins it back in roulette and offers it to Nick on the condition that he discourage Miralee's involvement with him. After a month of successfully keeping Miralee out of Basin Street, Nick determines to show her its sordid side to teach her a lesson. At dawn, assuring Nick she has no illusions about him, Miralee kisses him, and they are seen by her mother. Mrs. Smith appeals to her friend, Colonel McArdle, and he has an article printed about the dangers facing unchaperoned debutantes visiting Storyville. He also suggests to the Public Safety Commissioner that he condemn the district. One night, Nick orders Grace, who is drunk, to leave the club, and she is hit by a car and killed. The incident causes a grand jury to order that Storyville be evacuated by the United States Navy. Satchmo and his friends pack up and leave, and Nick makes plans to move to Chicago. Miralee begs Nick to take her with him, and in order to spare her feelings, he accepts an expensive bracelet from Mrs. Smith to make it look as if he never loved Miralee. He returns the bracelet to Henry Ferber, Miralee's music teacher, to give to Mrs. Smith, but she does not tell Miralee. Determined to give up the gambling business in favor of spreading jazz music across the nation, Nick opens the Club Orleans in Chicago, with Satchmo and piano player Meade Lux Lewis as performers of Chicago style blues. Meanwhile, Miralee becomes a famous opera singer in Europe. Eventually, Satchmo and Endie are married, and he and his band tour Europe. In Paris, Satchmo sees Miralee and tells her that Nick returned the bracelet and has been heartbroken ever since. He also tells her that Nick gave up gambling, has a new job as a music agent, and has been busy trying to introduce New York to the blues. Finally, at a concert at Symphony Hall, Miralee surprises Nick by including Woody Herman and his band and Satchmo and his band in the program. For an encore, Miralee sings Endie's old favorite, "New Orleans," for Nick.