Comcast Center is a skyscraper in Center City, Philadelphia, Pennsylvania, United States. The 58-story, 297-meter tower is the tallest building in Philadelphia and the state of Pennsylvania, as well as the twenty-first tallest building in the United States. Originally called One Pennsylvania Plaza when the building was first announced in 2001, the Comcast Center went through two redesigns before construction began in 2005. Comcast Center was designed by architect Robert A. M. Stern for Liberty Property Trust.