George B. Post, Mills Building, New York, 1881. Wrought Iron Portcullis. (Landau, Post)

While Post had taken his inspiration for the design of his Cornelius Vanderbilt II mansion from Hunt’s earlier chateauesque designs, his final design for the Mills Building seems to owe more to Snook’s William H. Vanderbilt palazzo.  In the final ten-story, 156′ high design of what can be considered to be the first large office building of the 1880s, Post completely abandoned his original ornate roofline, in favor of the overall box-like, palazzo form of the Shillito’s store.  He conversely reverted to the standard paired window and colossal Classical pilaster language of his office buildings of the 1870s, to arrange the elevation into a two-story stone base with the upper eight floors articulated into a 2:3:2:attic rhythm.   As he had done in the Western Union building, Post tried to make a transition in the second layer by alternating layers of the base’s brownstone with layers of red brick from the upper four floors that were sheathed in red brick and terra cotta (provided by Loring’s Chicago Terra Cotta).  It had the result of once again imparting an unnecessary busyness to that area of the building’s façade.  As in the Shillito’s Building, there were no arches in the facade of the Mills Building, except for the triumphal arched entry.  The Mills Building was another early example of a non-romantic, rational composition of a multistory façade (with applied Classical details).

George B. Post, Mills Building, New York, 1881. Note that all the windows have awnings. (Online)

Structurally, the building was typical “boxed” construction with its interior iron frame and exterior masonry bearing piers.  In the process of excavation, a body of quicksand was found within the site that forced the redesign of the building’s foundation.  I want to describe the building’s foundation simply to show that even New York City had sometimes presented builders with geologic problems, not unlike those faced by builders in Chicago.  Fearing that further excavation might cause adjacent buildings to settle because the quicksand would ooze into the excavation, lowering the bearing elevation of existing foundations, thereby causing portions of these buildings to settle more and possibly crack, Post redesigned the foundation to be a solid brick wall that at grade began at 3’ 6” in thickness, with a constant outward slope that reached 5’ in thickness, at 18’ below grade (remember in New York, in this case bedrock was at 65’ below grade, basements were not limited to only the first 12’ below grade as was the case in Chicago).  Here Post placed an 8’ wide continuous concrete pad under the wall.

Post, Mills Building. Floor Plans. (Landau, Post)

As he had eventually rejected the triple windows of the Shillito’s Building, Post also deviated from its plan.  As opposed to lining the perimeter of the site with single-loaded corridor offices around an interior atrium, as his initial scheme apparently had done, it is evident that by experimenting, Post realized he could create more rentable office space if he used two double-loaded corridors that were pushed to the short sides of the site and separated these with an exterior lightcourt, not at all unlike Snook’s entry in the W.H. Vanderbilt mansions and similar to how he had just designed the Post Building.  This created a highly efficient circulation scheme, symmetric about the centrally-located elevator core. (There also an extension wing built to provide on entrance on Wall Street.) The building’s footprint at grade was some 23,000 sq.ft., that resulted in almost 200,000 sq.ft. of rentable floor area.  This created over 300 offices that had a reported 800 tenants with 1500 employees in the building.  All of which could be served lunch in a restaurant located on the top floor.

Post, Mills Building. Entrance. Note the repetitive windows in front of the elevator bank on each floor. The grand staircase to the Entresol testifies to the importance of the second floor at this time (and could easily have been the influence for Root’s staircase in the Rookery’s atrium). The wrought iron portcullis was lowered at closing, thereby offering better night time security. (Online)

The lightcourt plan also vastly improved the natural lighting and ventilation of the internal office spaces, and also permitted a more flexible subdivision of each floor that could respond to a specific client’s needs.  This was accomplished with the use of lightweight hollow tile partitions that no longer needed to be placed directly over a beam for support.  The exterior exposure of the lightcourt also changed the proportions of the facade that now had a distinct vertical accent, while it also broke up the great mass of the entrance facade at its center that helped to emphasize the symmetrical location of the entrance.  Post located the entry lobby and hall directly under the skylight at the bottom of the lightcourt.  The first two floors were designed for banks, insurance and finance companies, for which a central grand staircase took visitors immediately up to the entresol.  For those visiting the upper floors, the lobby led directly to the bank of four elevators located at the rear of the building.  The building’s ornamental highlight had to have been the wrought iron portcullis that was hydraulically raised every morning in time for the start of the business day.

The reverse arch in the portcullis’ ironwork would complete a circle with the semicircular arch above. (Left: Online; Right: ClipArt ETC)

In 1883, in the basement that Post had created with the foundation, the building was the first to have its own electricity-generating plant, that supplied power for some 5,600 lights throughout the building.  (Thomas Edison had held the first public display of his new incandescent light bulb on December 31, 1879, that received its patent only a month later in January 1880.)  For good reason, Winston Weisman in an article in 1972 had identified the Mills Building as the first modern office building.  Darius Mills had brought the Palace Hotel’s “over-the-top” aesthetic (at $1.43 million it was the most expensive commercial building in New York to date, with cherry trimmed offices and corridors with tile floors and marble wainscotting) to the New York City speculative office building/skyscraper.  He and George Post had set the bar for the competition at a much higher level than what had existed prior to the Depression.  Nothing like this existed at this time in New York, let alone at the fringe of civilization in Chicago.


Landau, Sarah B. George B. Post, Architect.  New York: Monacelli Press, 1998.

Landau, Sarah B., and Carl Condit.  The Rise of the New York Skyscraper, 1865-1913. New Haven: Yale University Press, 1996.

Weisman, Winston, “The Commercial Architecture of George B. Post.” JSAH, Vol. 31 No. 3, Oct, 1972.

(If you have any questions or suggestions, please feel free to eMail me at: thearchitectureprofessor@gmail.com)

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