
After 1900, Sullivan's work consisted mainly of exquisitely designed banks, stores, and churches located in small towns throughout the Midwest. Among Sullivan's most renowned projects from this later period are the Schlesinger and Mayer Store (now Carson, Pirie, Scott & Co., 1898–18-1903) in Chicago, the Bayard-Condict Building (1897) in New York, and the facade of the Gage Building (1898–1899) in Chicago. Adler withdrew from the partnership in 1895 and, like Sullivan, continued to practice independently. Discontented with designing in the historical styles taught at the École des Beaux-Arts, Sullivan set out to create an architectural vocabulary that would reflect contemporary American culture. Sullivan is well known for his belief that a building's function should be clearly expressed in its form and structure. Their most renowned residential design was the commission for James Charnley on Astor Street in Chicago, which was completed in 1892. Louis, the Chicago Stock Exchange (1893–1894, demolished), and the Guaranty Building (1894-1895) in Buffalo, New York. Sullivan and Adler's work contributed to the development of the uniquely American building type, the skyscraper, and their partnership produced such remarkable structures as the Auditorium Building (1886–1889) in Chicago, the Wainwright Building (1890–1891) in St. For fourteen years this relationship produced buildings distinguished by both their design and engineering innovations. In 1879, Sullivan joined the respected engineer Dankmar Adler (1844–1900), who had been practicing in Chicago since 1866. Six months later, Sullivan left for Paris to study architecture at the École des Beaux-Arts, which was the leading school of architecture in the world. Louis Henry Sullivan was born in Boston and came to Chicago after the Great Chicago Fire of 1871 to join in the rebuilding effort. The ornament found throughout the interior and exterior of the building reflects both Sullivan's love of sinuous plant forms intertwined with underlying geometric forms and Wright's variations of these themes. The house is symmetrical in plan, with one room located on either side of the central atrium on each floor. The dramatic interior of the house is dominated by an atrium that soars from the first floor hall to a skylight two floors above. The exterior of Charnley House is a virtually unadorned brick and limestone facade that commands its corner location. It is a sign of Sullivan's admiration for Wright and a testament to their friendship and working relationship that the senior architect allowed his draftsman to become involved in the design process at all. With the Charnley House, Sullivan rejected the historical details common to Victorian architecture in favor of abstract forms that later became the hallmarks of modern architecture. The Charnley House, which has long been recognized internationally as a pivotal work of modern architecture, stands as evidence of the extraordinary power of Sullivan and Wright's creativity in collaboration.

Sullivan, Wright's architectural mentor, hired the younger man in 1887 as a draftsman to assist with producing construction drawings for the Auditorium Building (1887–1889) in Chicago. As a junior draftsman, Wright also assisted with residential commissions such as the James Charnley House (1891–1892). Louis Sullivan and Frank Lloyd Wright are major figures in American architecture.
