The skyscraper, like any other architectural form, had gone through a long period of evolution. During the mid 1800's buildings were generally less than four stories. In 1885, architect and builder, James Bogardus, forecasted that buildings were going to need to be extremely high in order to accommodate corporations and factories in cities. He constructed an eight story building in Chicago that is recognized as one of the first skyscrapers. Its frame was a strong and static iron cage that had a solid foundation at the bottom. This new and innovative idea led to an unbelievable growth in the height of buildings. Soon thereafter, architects switched over to the use of cast iron. However, cast iron was becoming unsuitable for such massive buildings. A new material, that had more strength, had to be used for these incredible structures. That is when the population of the steel industry began. Steel became so readily available, it seemed that new skyscrapers were shooting up in every city.
Today, the size of a city is judged by the height of its skyline. The size of a skyscraper often determines the wealth of the corporation that owns it. One of the tallest skyscrapers today is the Sears Tower in Chicago at 1,454 feet and 110 stories. The tallest self-supporting structure in the world is the CN Tower in Toronto, Ontario at 1,821 feet. Over the years, skyscrapers have revolutionized corporations, factories, and most importantly, the city. Corporations can have half of their employed workers, working in one building. Also, skyscrapers help boost the economy because big cities have become major vacation spots. The Empire State Building alone attracts 2.5 million visitors each year. In many ways, they have become an industry in themselves.