The Rookery was completed in 1888 and designed by Burnham and Root. The name may refer to pigeons that nested on a reservoir previously on the site, or to the temporary city hall that later stood there. The old city hall was nicknamed a rookery for the crows and pigeons that flocked to it and for the corrupt politicians it housed.
It has 12 stories and stands 181 feet tall. The exterior walls carry load, and there is an interior steel frame. Frank Lloyd Wright redesigned the lobby between 1905 and 1907, and William Drummond remodeled the building in 1931.
A two-story light court in white terracotta brings daylight to inside offices. Its skylight has 5,000 glass panes. It was designated a National Historic Landmark on May 15, 1975.