 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.