Penn Center is the heart of Philadelphia's Central Business District. It derives its name from the nearly five million square foot office and retail complex that helped transform it from a gritty industrial and low-rent commercial district into the centerpiece of Philadelphia's business district in the late 20th century. It is located between 15th and 19th Streets, east to west and from John F. Kennedy Boulevard to Market Street, north to south. It is credited with bringing Philadelphia into the era of modern office buildings. - Source: Wikipedia