The past commercial success of Nachusa House is reflected through the many changes to its design. The first addition to the hotel was in 1854 when the old west annex was added, this four story, 60 room structure was demolished during the 1950s and rebuilt as it appears today. In 1868 the mansard roof and fifth floor were added to the building; both features were important in solidifying the hotel's image as a first class hotel. Other architectural details were added and removed through the years, including the addition of a thin coat of stucco in the 1880s. In 1914 the building's south annex was added, though it was essentially gutted during the 1950s and very little of the original 1914 structure remains.