The early skyscrapers were a range of tall commercial buildings built between 1884 and 1945, predominantly in the American cities of New York City and Chicago. Cities in the United States were traditionally made up of low-rise buildings, but significant economic growth after the 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. Their numbers grew