The earliest stage of skyscraper design encompasses buildings built between
1884 and 1945, predominantly in the American cities of New York and Chicago.
Cities in the United States were traditionally made up of low-rise buildings,
but significant economic growth after the American Civil War and increasingly
intensive use of urban land encouraged the development of taller buildings
beginning in the 1870s. Technological improvements enabled the construction of
fireproofed iron-framed structures with deep foundations, equipped with new
inventions such as the elevator and electric lighting. These made it both
technically and commercially viable to build a new class of taller buildings,
the first of which, Chicago's 138-foot (42 m) tall Home Insurance Building,
opened in 1885.