As I first did in V.3 Sec. 4.9, let me recapitulate a number of different approaches to a “modern” skyscraper design that the Chicago School employed, that all fit within my definition:

1. Express the building’s structure, be it a bearing wall or a grid of columns and beams.

2. Express the building’s reliance on the columns. The columns were the dominant structural element (lose a beam, you lose a floor; lose a column, you lose everything supported above it). This was accomplished by recessing the spandrels in relation to the front of the columns so the columns were continuous from the ground.

3. Express the fact that the skyscraper was simply a large, rectangular volume of space. The exterior was no longer structural, but merely a uniform skin/veil/curtain that enclosed the interior space, therefore, the facade should be detailed so that it would be read as one continuous surface or enclosure of the interior volume (as if it was wrapped in cellophane). This skin could be all brick with glass windows or entirely made with only plates of glass. In either instance, the visual result would be a continuous material of uniform thickness applied to the exterior of the building’s structure.
These first three methods are “honest” expressions of the building’s “constructional” function. One could also choose to express the “building’s program’s” functions:

4. Express the fact that the skyscraper was an accumulation of identical floors, stacked one on top of the next. Therefore, the facade should consist of a repetition of horizontals, alternating between the spandrel beams of each floor, and the glass infill between these. This concept would only be possible using the iron frame, by cantilevering the floors beyond the face of the columns, allowing the horizontal lines of each floor to be the dominant elevational element.

5. If there were different types of uses contained with the building, i.e., rental floors, commercial floors, office space, residential space, public floors (restaurant or observatory), and mechanical floor, one could easily differentiate each function within the design of the elevation by giving it its own, distinctive elevational/window treatment and/or floor height.
Or an architect could see his/her problem as the creation of a building whose function was to be architecturally artistic or meaningful.

6. The best example of this idea, in my opinion was Sullivan’s Wainwright Building. Sullivan thought that the skyscraper’s proportions were overwhelmingly vertical, so why not reinforce the skyscraper’s overall massing by accentuating its verticality through emphasizing the continuity of its columns. The skyscraper’s function was to soar, as he stated in his 1896 essay, “The Tall Building Artistically Considered:”
“What is the chief characteristic of the tall office building? And at once we answer, it is lofty… It must be tall, every inch of it tall… It must be every inch a proud and soaring thing, rising in sheer exultation that from bottom to top it is a unit without a single dissenting line.”
So inspired, he detailed his first towers with repetitive vertical elements that gave their exteriors a “soaring” expression such as his design for the Wainwright Building. This was not an “honest” solution because every other “column” in its façade is not a structural column but a mechanical run, even though they are detailed to look the same. The word “express” in architecture has an artistic or poetic side that allows for the architect to blur the literal meaning of the word “express” in the employment of his/her “artistic license,” such as Sullivan was prone to do. For Sullivan, this building’s “function” was to soar, which he expressed in his designs. Therefore, having expressed the building’s function, Sullivan’s designs do qualify to be called Chicago School.
What was slowly evolving, (that is the precise meaning of the word, isn’t it?) initially, in Chicago by July 1888 was an approach to the design of skyscrapers that did not imitate traditional architectural design parameters/styles/details, but synthesized the functional, logical and/or lyrical determinates of a given architectural problem into a new architectural aesthetic that also sported a corresponding new ornamental language. In a number of public talks, both Root and Sullivan agreed that a new architectural style could not be invented, but would have to evolve over time. Sullivan, and to a lesser extent, Root, were, at the same time, evolving their own ornamental language free from historical precedents. These two issues would slowly evolve during 1888-1891, in a slow, but rather methodical process until Root and Sullivan had synthesized both issues into a new language: the Chicago School. One could call it a “thoroughly modern” style of architecture. (Note I called it “a modern style” and not “the modern style”, for I maintain that there were and still are a number of modern styles of architecture, as there are a number of “Classical,” “Romanesque,” and “Gothic” styles of architecture. I also did not call it nor attempt to make any connection with the term “modernistic”, the word used by those historians who only recognize the “International Style” of the 1950s as the only attempt to evolve a modern architecture, either in a supportive or in a critical manner.)
As early as August 1891, America’s leading critic, Montgomery Schuyler in an article for Harper’s New Monthly, “Glimpses of Western Architecture: Chicago” had recognized and identified the difference that these architects were achieving with their new methodology:
“These buildings… not merely attest the skill of their architects, but reward their self-denial in making the design for a commercial building out of its elements, however unpromising these may seem; in permitting the building, in a word, to impose its design upon them, and in following its indications, rather than in imposing upon the building a design derived from anything but a considerations of its own requirements. Hence it is that, without showing anywhere any strain after originality, these structures are more original than structures in which such a strain is evident. “The merit of originality is not novelty; it is sincerity.” The designer did not permit himself to be diverted from the problem in hand by a consideration of the irrelevant beauties of Roman theatres, or Florentine palaces, or Flemish town-halls, and accordingly the work is not reminiscent of these nor of any previous architectural types, [my emphasis] of which so many contemporary buildings have the air of being adaptations under extreme difficulties. It is to the same directness and sincerity in the attempt to solve a novel problem that these buildings owe what is not their least attraction, in the sense that they convey of a reserved power. The architect of a commercial palace seems often to be discharging his architectural vocabulary and wreaking his entire faculty of expression upon that contradiction in terms… There is something especially grateful and welcome in turning from one of them to a building like one of those now in question, which suggests by comparison that, after he had completed the design of it, the architect might still had something left–in his portfolios and in his intellect.”
FURTHER READING:
Leslie, Thomas. Chicago Skyscrapers: 1871-1934. Urbana: University of Illinois, 2012.
Schuyler, Montgomery. American Architecture-Studies, Harper & Bros: New York, 1892.
(If you have any questions or suggestions, please feel free to eMail me at: thearchitectureprofessor@gmail.com)