Commerce Square is a Class-A, high-rise office building complex in the Central Business District of Philadelphia, Pennsylvania, United States. Commerce Square consists of One and Two Commerce Square, two identical 41-story office towers 565 feet (172 m) high that surround a paved courtyard of 30,000 square feet (2,800 m²). 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. The towers were built as part an office-building boom Philadelphia was experiencing on West Market Street in the late 1980s. Designed by IM Pei & Partners (now called Pei Cobb Freed & Partners), the towers were developed in a joint venture between Maguire Thomas Partners and IBM. IBM also leased more than half of One Commerce Square for the company's Mid-Atlantic headquarters. Construction of the first phase, which included One Commerce Square, the plaza, and retail space, began in 1985 and was completed in 1987. The project's second phase, Two Commerce Square, did not begin until a lead tenant was secured for the building in 1990. Consolidated Rail Corporation (Conrail) agreed to be Two Commerce Square's lead tenant and make the skyscraper its corporate headquarters after a two-year search for office space in the region.