Ethnic and national dialects were a popular source of comedy not only on the variety stage, but also in legitimate plays from the 1890s to the 1930s, when immigrants were coming to the United States in record numbers. Before the racial integration of the American stage in the 1920s, African American characters were portrayed by white actors in blackface using linguistic clichés. Similarly, the stage Irishman or Irish cook and the stage Jew were portrayed largely through exaggerated speech patterns and vocabularies. Dialect comedians were consistently popular in musical and vaudeville entertainment into the 1930s.
See also ethnicity in American drama.
The Historical Dictionary of the American Theater. James Fisher.