The architects Burnham & Root moved their offices here for a while upon its completion, and Frank Lloyd Wright also set up an office here at one time.
The metal framework is a combination of cast iron (main columns), wrought iron (spandrel beams), and steel (internal columns).
The lobby was remodeled in 1905 by Frank Lloyd Wright, who simplified the ironwork and added planters and light fixtures in his characteristic style.
Before the Rookery name had stuck to this project, its developers proposed a long list of possible names, mostly of American Indian derivation.
The Rookery represents a transition between masonry and metal construction methods, with the outer walls supported mostly by masonry piers and the inner frame built of steel and iron.
Architect John Root devised the "grillage foundation" - iron rails and structural beams in a crisscross pattern and encased in concrete - to support the building's immense weight without heavy foundation stones.
Since the interior frame is built of steel and iron, the facade facing the light court has far more extensive window area than the more fortresslike street facades.
An atrium, originally an open light court, extends through the center of the building, down to the lobby skylight. On the west side of this court there is a famous semi-spiral staircase.
The building became an official city landmark in 1972.
Like the Fisher Building the Rookery incorporates in its facade animal forms derived from the building's name - in this case pairs of rooks by the entrance archway.
The only metal framing on the perimeter walls is in the first two stories along the alleys. Above that the walls are pure masonry.
The exterior ornamentation draws from several styles, including Romanesque, Moorish, Islamic, and Venetian.
The light court was very influential in the design of office buildings in Chicago, including its use of glazed white brick for added brightness.
Since the perimeter walls are so much heavier than the interior frame, their foundations were built higher to account for greater settling.
The renovation architects were recognized with an Honor Award for Design from the American Institute of Architects in 1993.
Above the LaSalle Street and Adams Street entrances there are wide balconies at the 8th floor.
The "Rookery" name is inherited from the previous building on this site, an old city hall which was a favorite roosting spot of pigeons.
Completed in 1888, the Rookery is the oldest high-rise in Chicago that is still standing.
In the Frank Norris novel The Pit, financial speculator Curtis Jadwin's has his office in the Rookery.
Projected string courses around the facade divide the building into five distinct horizontal layers.
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