The first major playwright to break the operetta mold was George M. Cohan, who wrote librettos about working class, Irish-Americans fighting and triumphing over the odds stacked against them.  His major shows include Little Johnny Jones (1904.42), Forty-Five Minutes from Broadway (1906.02), George Washington, Jr. (1906.11), Fifty Miles from Boston (1908.09) and Little Nellie Kelly (1922.43).  It is interesting to note that some of the music from Little Nellie Kelly was used in the Judy Garland film of the same name.