The Auditorium Building in Chicago marked the first period of Sullivan’s design maturity

The initial stage of Sullivan's development as a designer began with his acceptance of the commission to create the Auditorium Building in Chicago in 1886. This proposal was an unusual union of a hotel and office building encircling a theater with 3,982 seats for opera.

It is a granite and limestone structure with a 17-story tower that was finished in December 1889. It is 10 stories tall. The Marshall Field Wholesale Store design by architect Henry Hobson Richardson, which had just been finished in Chicago at the time, is heavily influenced by the noble arcaded exterior's plain profile, lack of adornment, and arched design.

However, the interior is elaborately embellished with relief ornament and painted stenciled patterns, showcasing Sullivan's extraordinary flair for ornament creation. The auditorium's interior, which was rebuilt in 1967, is especially lavish and includes gilded plasterwork and innumerable electric light bulbs. The spectacular and appropriately theatrical decoration owes nothing to historical eclecticism. Adler, who was in charge of the building's whole structural and mechanical design, is also responsible for the auditorium's astoundingly successful acoustical design.