[6] In August 2017, Buck and Northern Trust announced an agreement for the bank to lease 465,000 square feet (43,200 m2) of the building.

The lease, which includes signage and naming rights, will consolidate approximately 2,500 to 3,000 Northern Trust workers from several sites around Chicago and take place in 2020.

[citation needed] The company's previous headquarters from 1943 to 1962 had been Metropolitan Tower (310 South Michigan Avenue, aka Continental Center I).

CNA Financial, a property insurance company, later paid $18 million to settle the resultant lawsuit.

Building engineers use a computer program to plot which windows need to be lighted to create the proper message.