Aon Center (Chicago)

There is also an Aon Center in Los Angeles, California, see Aon Center (Los Angeles).

The Aon Center (200 East Randolph Street) in Chicago was completed in 1972. At 1,136 feet (346.3 m) tall, it is second only to the Sears Tower in height in Chicago. When the building was originally built, it was the world's tallest marble clad building. Eventually, the harsh climate caused the building's Carrara marble sheathing to fail and detach from the building. From 1990 to 1992, the entire building was refaced with white granite at a greater expense than the original cost of the whole structure. The building employs a tubular steel-framed structural system with V-shaped perimeter columns to resist earthquakes, reduce sway, minimize column bending, and maximize column-free space.

The Standard Oil Building or "Big Stan" as the building was often called, was known officially as the Amoco Building. After the building was sold, it became known officially as the Aon Center.

In the early 1980s, the lights in selective offices in the building were turned on to form a huge cross in the Christmas season.