Dome

Base of the east elevation; The seventeen-story building stands 197 feet (60 meters) tall. The northern half was designed and built by Burnham & Root in 1889-1891; the southern half was designed and built by Holabird & Roche in 1891-1893. The building was designated a Chicago Landmark on November 14, 1973 and was also listed on the National Register of Historic Places. The southern half of the building was built using the more technologically advanced steel frame construction, which allowed narrower piers and wider windows. The radical difference in construction between the two halves marks the building's place in architectural history at the end of one building tradition and the beginning of another. Source: Wikipedia; http://en.wikipedia.org/wiki/Main_Page (accessed 7/17/2010)