The John Hancock Center is a 100-story, 1,128-foot supertall skyscraper located on Magnificent Mile, Chicago, Illinois. When the building topped out on May 6, 1968, it was the second-tallest building in the world, the tallest in Chicago, and the tallest outside New York City. It is currently the fifth-tallest building in Chicago and the thirteenth-tallest in the United States.
The 100-story skyscraper was designed by architect Bruce Graham and structural engineer Fazlur Khan of Skidmore, Owings, & Merrill and soars 1, 127-feet into the sky. It was the world’s first mixed-use high-rise, containing offices, restaurants, and the third highest residence in the world with approximately 700 condominiums. One of the most famous buildings of the structural expressionist style, the skyscraper’s distinctive X-braced exterior shows that the structure’s skin is part of its “tubular system”. This is one of the engineering techniques which the designers used to achieve a record height; the tubular system is the structure that keeps the building upright during wind and earthquake loads. Due to the high winds in Chicago, one of the main factors that had to be taken into consideration was using a secure structure for the building that would minimize movement on windy days. This X-bracing allows for both higher performance from tall structures and the ability to open up the inside floorplan. Although the X-bracing is massive and slightly blocks views from the interior, it is the Hancock Building’s signature exterior feature and is structurally sound.
The tower’s tapered shape was chosen in order to match the different floor space requirements that decrease from bottom to top — from the entrance and commercial zones at the base to the clusters of small apartments at medium height and finally to the large apartments on top, where relatively less space is needed for ancillary rooms with artificial lighting.
On the 95th story is the John Hancock Observatory with Chicago’s only open-air SkyWalk that was built with steel casing approved by NASA. Popular for tourists, the observatory competes with Willis Tower’s Skydeck, offering views of the city from every angle, including gorgeous shots of Lake Michigan and on a clear day the sights of four other states. Halfway up the building on the 44th floor also lies America’s highest swimming pool. With both of these features, along with an astonishing height of 1,506-feet when measured to the top of its two identical antennas, the John Hancock Center is the quintessential model of a brilliantly engineered skyscraper that adds beauty through its symmetry to the skyline, making it one of Chicago’s finest works of architecture.