Which kinds of buildings gave Adler and Sullivan their greatest architectural influence?

While Adler and Sullivan completed a variety of residential projects, it was their commercial work that established their significant art-historic contribution.1

The firm’s greatest influence is most notably associated with the development of the skyscraper. During the commercial expansion of the 1880s in Chicago, Sullivan sought to solve the challenge of giving visual expression to the height of tall buildings, moving away from unsuitable historical styles toward a "proud and soaring" unity. Key examples of this influence include:21

• The Wainwright Building: Located in St. Louis, this structure is considered Sullivan's most important skyscraper. It utilized a steel frame and emphasized vertical elements to create a cohesive, soaring design.1
• The Guaranty Building: Similar in concept to the Wainwright, this Buffalo landmark is noted for its decorative terra-cotta surface.1
• The Auditorium Building: This project marked a period of design maturity for Sullivan, combining a hotel and office block with a massive, acoustically advanced theatre.1

Through these commercial designs, Sullivan pioneered the idea that a building's form should express its function and structural basis, a philosophy central to his architectural legacy.12