The Depression of 1873 dried up much of Furness’s work, and he was forced to let Sullivan go. Sullivan moved to Chicago in 1873 to take part in the building boom following the Great Chicago Fire of 1871. He worked for William LeBaron Jenney, the architect often credited with erecting the first steel frame building. After less than a year with Jenney, Sullivan moved to Paris and studied at the École des Beaux-Arts for a year. He returned to Chicago and began work for the firm of Joseph S. Johnston & John Edelman as a draftsman. Johnston & Edleman were commissioned for the design of the Moody Tabernacle, and had the interior decorative fresco secco stencils (stencil technique applied on dry plaster) designed by Sullivan. In 1879 Dankmar Adler hired Sullivan. A year later, Sullivan became a partner in Adler’s firm. This marked the beginning of Sullivan’s most productive years.

The young Wright, by contrast, was Sullivan’s protégé for seven years, beginning in 1887, when Sullivan was at the height of his fame and power. The two architects would sever their ties in 1894 due to Sullivan’s angry reaction to Wright’s moonlighting in breach of his contract with Sullivan, but Wright continued to call Sullivan “lieber Meister” (“beloved Master”) for the rest of his life. After decades of estrangement, Wright would again become close to the now-destitute Sullivan in the early 1920s, the time when Roark first comes under the likewise impoverished Cameron’s tutelage in the novel. Wright, however, was now in his fifties. Nevertheless, both the young Roark and middle-aged Wright had in common at that time that they both faced a decade of struggle ahead. After the triumphs earlier in his career, Wright came increasingly to be viewed as a has-been, until he experienced a renaissance in the latter half of the 1930s with such projects as Fallingwater and the Johnson Wax Headquarters.

In 1890 Sullivan was one of the ten U.S. architects, five from the east and five from the west, chosen to build a major structure for the “White City”, the World’s Columbian Exposition, held in Chicago in 1893. Sullivan’s massive Transportation Building and huge arched “Golden Door” stood out as the only building not of the current Beaux-Arts style, and with the only multicolored facade in the entire White City. Sullivan and fair director Daniel Burnham were vocal about their displeasure with each other. Sullivan later claimed (1922) that the fair set the course of American architecture back “for half a century from its date, if not longer.” His was the only building to receive extensive recognition outside America, receiving three medals from the French-based Union Centrale des Arts Decoratifs the following year.

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.

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.

By both temperament and connections, Adler had been the one who brought in new business to the partnership, and following the rupture Sullivan received few large commissions after the Carson Pirie Scott Department Store. He went into a twenty-year-long financial and emotional decline, beset by a shortage of commissions, chronic financial problems, and alcoholism. He obtained a few commissions for small-town Midwestern banks (see below), wrote books, and in 1922 appeared as a critic of Raymond Hood’s winning entry for the Tribune Tower competition.

He died in a Chicago hotel room on April 14, 1924. He left a wife, Mary Azona Hattabaugh, from whom he was separated. A modest headstone marks his final resting spot in Graceland Cemetery in Chicago’s Uptown and Lake View neighborhood. Later, a monument was erected in Sullivan’s honor, a few feet from his headstone.

More recent study of Rand’s posthumously published journal notes, as well as a close comparison of the respective careers of the real and fictional architects by Heynick, has explored this connection in some detail. Although Rand’s journal notes contain in toto only some 50 lines directly referring to Sullivan, it is clear from her mention of Sullivan’s Autobiography of an Idea (1924) in her 25th-anniversary introduction to her earlier novel We the Living (first published in 1936, and unrelated to architecture) that she was intimately familiar with his life and career. The term “the Fountainhead,” which appears nowhere in Rand’s novel proper, is found twice (as “the fountainhead” and later as “the fountain head”) in Sullivan’s autobiography, both times used metaphorically.

After Nickel’s death, in 1972 the Richard Nickel Committee was formed, to arrange for completion of his book, which was published in 2010. The book features all 256 commissions of Adler and Sullivan. The extensive archive of photographs and research that underpinned the book was donated to the Ryerson and Burnham Libraries at The Art Institute of Chicago. More than 1,300 photographs may be viewed on their website and more than 15,000 photographs are part of the collection at The Art Institute of Chicago. As finally published, the book, The Complete Architecture of Adler & Sullivan, was authored by Richard Nickel, Aaron Siskind, John Vinci, and Ward Miller.

The Guaranty Building Interpretive Center in Buffalo, on the first floor of the building now owned and occupied by the law firm Hodgson Russ, LLP, opened in 2017. The exhibit space was financed by Hodgson Russ, LLP, and co-designed by Flynn Battaglia Architects and Hadley Exhibits. It features a scale model of the building by David J. Carli, Professor of Engineering at the State University of New York at Alfred. The Center’s exhibits were donated to Preservation Buffalo Niagara. The Center, the only museum dedicated to Sullivan, is open to the public.