In 1984, the unwritten Gentleman’s Agreement that forbade building above the 548-foot-high statue of William Penn atop City Hall was about to be eliminated when, in April, developer Willard Rouse proposed a skyscraper development that eventually became Liberty Place. The proposal apparently influenced more developers and architects to build towers above the former height limit. The Commerce Square twin towers were revealed at 2005 Market Street in Center City at the end of the year. Designed by I.M. Pei and Partners and developed by IBM and Maguire/Thomas Partners, the 41-story towers were not built simultaneously, as One Commerce Square was the first building finished in the complex.
The project was announced on November 13, 1984, and images of the design were shared by The Philadelphia Inquirer on December 2. The towers were shown to rise slightly above City Hall to a height of 565 feet, once again stirring outrage among those opposed to towers that would rise above the unofficial height limit. The first building was projected to start in June 1985 and complete construction in early 1987. The groundbreaking took place on June 10, 28 days after the groundbreaking of One Liberty Place. At the very end of July, the development team announced that only one building was to be constructed at a time. The steel structure started rising shortly after.
The steel structure was well underway by the end of 1985, and the tower was shooting upward by early 1986. One Liberty Place already stood above ground at the time, but One Commerce Square has topped out its diamond topped crown on June 6, 1986, ahead of the former. The east diamond was the last structural piece placed on top of the tower, and the crane was taken down by the next month. The exterior was completed by the end of 1986, and the building opened on October 23, 1987. Two Commerce Square was projected to start in the next year, but was delayed for a few more years.