stylistic:style_transfer, linguistic:voice_change, structural:expansion
Sullivan and the steel high-rise

Prior to the late nineteenth century, the weight of a multi-story building had to be supported principally by the strength of its walls. The taller the building, the more strain this placed on the lower sections of the building; since there were clear engineering limits to the weight such "load-bearing" walls could sustain, tall designs meant massively thick walls on the ground floors, and definite limits on the building's height.

The development of cheap, versatile steel in the second half of the nineteenth century changed those rules. America was in the midst of rapid social and economic growth that made for great opportunities in architectural design. A much more urbanized society was forming and the society called out for new, larger buildings. The mass production of steel was the main driving force behind the ability to build skyscrapers during the mid-1880s. By assembling a framework of steel girders, architects and builders could create tall, slender buildings with a strong and relatively lightweight steel skeleton. The rest of the building elements—walls, floors, ceilings, and windows—were suspended from the skeleton, which carried the weight. This new way of constructing buildings, so-called "column-frame" construction, pushed them up rather than out. The steel weight-bearing frame allowed not just taller buildings, but permitted much larger windows, which meant more daylight reaching interior spaces. Interior walls became thinner, which created more usable (and rentable) floor space.

Chicago's Monadnock Building (not designed by Sullivan) straddles this remarkable moment of transition: the northern half of the building, finished in 1891, is of load-bearing construction, while the southern half, finished only two years later, is of column-frame construction. While experiments in this new technology were taking place in many cities, Chicago was the crucial laboratory. Industrial capital and civic pride drove a surge of new construction throughout the city's downtown in the wake of the 1871 fire.

The technical limits of weight-bearing masonry had imposed formal as well as structural constraints; suddenly, those constraints were gone. None of the historical precedents needed to be applied and this new freedom resulted in a technical and stylistic crisis of sorts. Sullivan addressed it by embracing the changes that came with the steel frame, creating a grammar of form for the high rise (base, shaft, and cornice), simplifying the appearance of the building by breaking away from historical styles, using his own intricate floral designs, in vertical bands, to draw the eye upward and to emphasize the vertical form of the building, and relating the shape of the building to its specific purpose. All this was revolutionary, appealingly honest, and commercially successful.

In 1896, Louis Sullivan wrote:

It is the pervading law of all things organic and inorganic, of all things physical and metaphysical, of all things human, and all things super-human, of all true manifestations of the head, of the heart, of the soul, that the life is recognizable in its expression, that form ever follows function. This is the law. (italics in original)

" Form follows function " would become one of the prevailing tenets of modern architects.

Sullivan attributed the concept to Marcus Vitruvius Pollio, the Roman architect, engineer, and author, who first asserted in his book, De architectura (On architecture), that a structure must exhibit the three qualities of firmitas, utilitas, venustas – that is, it must be "solid, useful, beautiful." This credo, which placed the demands of practical use equal to aesthetics, later would be taken by influential designers to imply that decorative elements, which architects call "ornament", were superfluous in modern buildings, but Sullivan neither thought nor designed along such dogmatic lines during the peak of his career and this credo never put one concept above another. While his buildings could be spare and crisp in their principal masses, he often punctuated their plain surfaces with eruptions of lush Art Nouveau or Celtic Revival decorations, usually cast in iron or terra cotta, and ranging from organic forms, such as vines and ivy, to more geometric designs and interlace, inspired by his Irish design heritage. Terra cotta is lighter and easier to work with than stone masonry. Sullivan used it in his architecture because it had a malleability that was appropriate for his ornament. Probably the most famous example of ornament used by Sullivan is the writhing green ironwork that covers the entrance canopies of the Carson Pirie Scott store on south State Street.

Such ornaments, often executed by the talented younger draftsmen in Sullivan's employ, eventually would become Sullivan's trademark; to students of architecture, they are instantly recognizable as his signature.

Another signature element of Sullivan's work is the massive, semi-circular arch. Sullivan employed such arches throughout his career—in shaping entrances, in framing windows, or as interior design.

All of these elements are found in Sullivan's widely admired Guaranty Building, which he designed while partnered with Adler. Completed in 1895, this office building in Buffalo, New York is in the Palazzo style, visibly divided into three "zones" of design: a plain, wide-windowed base for the ground-level shops; the main office block, with vertical ribbons of masonry rising unimpeded across nine upper floors to emphasize the building's height; and an ornamented cornice perforated by round windows at the roof level, where the building's mechanical units (such as the elevator motors) were housed. The cornice is covered by Sullivan's trademark Art Nouveau vines and each ground-floor entrance is topped by a semi-circular arch.

Because Sullivan's remarkable accomplishments in design and construction occurred at such a critical time in architectural history, he often has been described as the "father" of the American skyscraper. But many architects had been building skyscrapers before or as contemporaries of Sullivan; they were designed as an expression of new technology. Chicago was replete with extraordinary designers and builders in the late years of the nineteenth century, including Sullivan's partner, Dankmar Adler, as well as Daniel Burnham and John Wellborn Root. Root was one of the builders of the Monadnock Building (see above). That and another Root design, the Masonic Temple Tower (both in Chicago), are cited by many as the originators of skyscraper aesthetics of bearing wall and column-frame construction, respectively.