American musical theater came of age with the 1927 production of Show Boat. In a striking departure from the earlier traditions of musical comedies and splashy but superficial revues, Show Boat dared to stage realistic, human characters in often disappointing circumstances: failed marriages, prejudice, the passing of time. More importantly, and even more daring, was the show's portrayal of the harsh life faced by Southern blacks. The very opening chorus establishes the racial themes, by contrasting the white socialites' excitement over the arrival of the steamboat "Cotton Blossom" to the drudgery of the black shoreworkers' duties loading bales of cotton. Both the musical and the novel by Edna Ferber on which it is based also confront the issue of miscegenation in the challenges faced by one of the main characters when her mulatto heritage is revealed. Jerome Kern and the lyricist Oscar Hammerstein II underscored the musical's racial themes by closing the entire show with a reprise of the first act's leitmotif, the song "Ol' Man River."
"Ol' Man River," thus treated as the show's unifying theme, is a melody first sung by one of the African-American dockworkers. The young daughter of Cap'n Andy has met a charming young man, and asked the Negro named Joe where she can find her friend Julie. Joe responds that she would be better to ask the "ol' river," because "he knows all about everything." Leaning on a bale of cotton, Joe then sings this song, Kern's replica of an African-American work song. Joe's aria moves forward with a rhythm relentless as the river's flow, or the weary feet of those who must "tote that barge and lift that bale." Yet the river, he sings, continues its rolling when those who plant are forgotten, and those who "sweat and strain" have long become sick of trying to live. The full chorus of Negro workers joins in the song, singing that they'd all like to escape "de white man boss," and cross that River Jordan. The flow of the Mississippi becomes the flow of time toward death and new life in the musical Show Boat, and it closes the play 50 years later in the characters' lives.
"Ol' Man River" became a showpiece for the many fine baritones who have sung it: Paul Robeson made it famous in the 1927 Ziegfeld production and the first film (1936), and William Warfield re-introduced America to "Ol' Man River" in the 1951 MGM film.