Following early success with the Five Flags Center in Dubuque, Iowa, the new firm quickly specialized in theatres.
In 1926 Paramount Pictures bought a controlling interest in Balaban & Katz, after which the Rapp office gained a national practice.
The firm diversified its practice away from theatres during the 1930s, and designed a variety of commercial and industrial projects.
[5] The Rapp brothers were among a group of highly influential American theatre architects, which also included Thomas W. Lamb of New York City and John Eberson of Chicago.
They designed many movie palaces, including a number of atmospheric theatres, which utilized romantic architectural elements to evoke specific times and places.
Many of the theatres and other buildings designed by the Rapp brothers have been listed on the United States National Register of Historic Places.