The Sears Tower commissioned by Sears, Roebuck and Company was with a height of 442 metres the tallest building in the United States since 1973. In February 1982, two television antennas were added to the structure, increasing its total height to 520 metres. It was designed by chief architect Bruce Graham and structural engineer Fazlur Khan of Skidmore, Owings and Merrill. The building consists of nine framed tubes taken together into one building. The nine tubes all reach forty-nine stories. At that point, two tubes end. The other tubes rise up to the sixty-fifth floor. From the sixty-sixth to the ninetieth floor, the tower has the shape of a crucifix. Only two tubes rise up to the full height. The tower looks different from every side and this construction withstand the strong Chicago wind, as each tube only needs to take a part of the pressure. The building's official address is 233 South Wacker Drive, Chicago, Illinois 60606.