Sears, which needed of office space for its planned consolidation and predicted growth, commissioned architects Skidmore, Owings & Merrill (SOM). Their team of Colombian-Peruvian architect Bruce Graham and Bangladeshi-Pakistani structural engineer Fazlur Rahman Khan designed the building as nine square "tubes" (each essentially a separate building), clustered in a 3×3 matrix forming a square base with sides. All nine tubes would rise up to the 50th floor of the building, where the northwest and southeast tubes terminate. The northeast and southwest tubes reach the 66th floor; the north, east, and south tubes end at the 90th. The remaining west and center tubes reach 108 floors.