Since the mid-19th cent. there had been repeated attempts to assimilate modern technology in practice and theory and to formulate a modern style of architecture suitable to its age. A functionalist approach eventually replaced the formerly eclectic approach to design. Technical progress in the use of iron and glass made possible the construction of Sir Joseph Paxton's celebrated Crystal Palace in London (1851), in which a remarkable delicacy was achieved. In the ensuing years iron, steel, and glass enabled architects and engineers to enclose the vast interior spaces of train sheds, department stores, and market halls, but often the structural forms were clothed with irrelevant ornament.
As late as 1889 the exposed, iron skeleton of the newly erected Eiffel Tower in Paris was met with public outrage. In Chicago, William Le Baron Jenney pioneered the use of a complete steel skeleton for the urban skyscraper in his Home Insurance Building (1883–85). His contemporary, Louis Henry Sullivan, first articulated the theory of functionalism (see functionalism), which he demonstrated in his numerous commercial designs. In addition, experiments in concrete construction were being carried out in France by François Hennebique and Auguste Perret, and in the United States by Ernest Ransome.
As a result of these advances, the formal conception of architecture was also undergoing a profound transformation. Frank Lloyd Wright, a pupil of Sullivan, experimented with the interpenetration of interior and exterior spaces in his residential designs. In Holland, where Wright's work was widely admired, the architects of de Stijl sought to organize building elements into new combinations of overlapping and hovering rectangular planes.