The lead role was intended for Lanny Ross, but Bing Crosby was cast because he was the more popular star instead. In fact, the songs were also selected especially for Ross, even though Crosby sings them in the final cut.
When Bing Crosby was cast, he requested another song be added. However, Richard Rodgers and Lorenz Hart had already returned to New York. The song, "It's Easy To Remember", was composed by the duo back east and they then sent a demo record back to Hollywood. It wound up becoming the film's biggest hit.
Booth Tarkington's story was actually a play, "Magnolia," which opened at the Liberty Theatre in New York on 27 August 1923 and closed in October 1923 after 40 performances. In the opening night cast were Leo Carrillo as "Tom" and Elizabeth Patterson as "Madame Rumford."
The story is set in 1851, the year that Stephen Foster composed "Old Folks at Home" (later more popularly known as "Swanee River"). The riverboat piano player tells Commodore Jackson, who says he's never heard it before, that the song is new.