Architecturally, the granite-clad towers feature setbacks on the north and south sides of the building and are topped with a pair of stone diamonds with cutout squares in the center.

IBM moved some of its operations out of Philadelphia in the early 1990s, and Conrail was bought by Norfolk Southern Railway and CSX Transportation later in the decade.

Renowned Philadelphia urban planner Edmund N. Bacon praised Commerce Square and its plaza by saying it "will prove to be one of the finest commercial projects to be built in this century".

IBM also agreed to serve as the lead tenant for One Commerce Square, occupying about half the building as its headquarters for the Mid-Atlantic region.

Plans for Commerce Square were officially announced on November 16, 1984 at a press conference held by Maguire and IBM at the Bellevue-Stratford Hotel.

The first phase of the project included One Commerce Square, retail and restaurant space, a plaza, and an underground parking garage.

[7] On March 30, 1990, after being sought after by numerous developers in Philadelphia and its suburbs, Conrail announced that it would be leasing 27 floors of Two Commerce Square.

In 1993 IBM, struggling financially, was shrinking its workforce and consolidating its operations nationwide, and its plans included moving some of its local employees out of the city.

[15] Philadelphia Plaza Associates emerged from bankruptcy reorganization early in 1998, but the company still had concerns about filling the space soon to be vacated by Conrail.

Between 1999 and 2000, as Conrail offices were phased out of Two Commerce Square, Thomas Properties filled the newly vacated space with new tenants.

[16][17] Located on West Market Street in Center City Philadelphia, Commerce Square comprises twin 41-story[nb 1] 565 feet (172 m) office towers designed by Henry N. Cobb and Douglas Gardner of IM Pei & Partners.

The Philadelphia Inquirer said "Its most positive aspect is that it avoids the developers' cliches of atriums and shopping malls and makes a real urban place.

"[26] Renowned Philadelphia urban planner Edmund N. Bacon praised Commerce Square and its plaza by saying "[Olin's] sensitivity for urban design is beautifully demonstrated by his design for the lobby level, including the splendid garden, of Commerce Square at 20th and Market streets, which I think will prove to be one of the finest commercial projects to be built in this century.

IBM initially occupied nearly half of One Commerce Square, but in the decades since, consolidation has reduced the company's presence in the building.