Part 1: Background and the History of Skyscrapers
By the early 1970s, when Citibank began plans for a huge new headquarters tower in midtown New York, the art of designing and building a strong, safe skyscraper seemed nearly perfected.
The skyscraper, like any other architectural form, had gone through a long period of evolution. After Elisha Otis's successful introduction of the first safety-brake-equipped elevator in the 1850s and the introduction of steel-frame construction, buildings began to grow upward. In 1910, the Metropolitan Life building broke all records for height until that time: it was 50 stories high.
By the 1930s, with the construction of the 102-story Empire State Building, skyscrapers, thanks to their widespread success, had begun to sprout in many cities worldwide. Areas populated with these tall buildings found themselves growing, literally, ever upward. The skyscraper, coupled with the introduction of modern, efficient subway systems in cities like New York, made it possible for companies to employ workforces unprecedented in size. Consequently, city populations increased immensely.
By 1930, daring, creative architects and engineers had even begun to depart from what had been accepted as the "traditional" method of designing and constructing skyscrapers. Innovations in skyscraper design such as lighter materials, increased window area, and cantilevered supports, resulted in taller, lighter, and slimmer buildings. For instance, Chicago's record-breaking Hancock Building, incorporating an innovative system of diagonal bracing (pictured in detail on this page) that allowed the building to be much leaner and lighter than it could be if it had been constructed in a traditional manner.