Philadelphia is one of America’s most important historical cities. Sometimes known colloquially as Philly, Philadelphia is the largest city in the U.S. state and Commonwealth of Pennsylvania, and the sixth-most populous U.S. city, with a 2017 census-estimated population of 1,580,863. Since 1854, the city has been coterminous with Philadelphia County, the most populous county in Pennsylvania and the urban core of the eighth-largest U.S. metropolitan statistical area, with over 6 million residents as of 2017.At Independence Hall on July 4, 1776, the Declaration of Independence was adopted, and in September 1787, the Constitution was drafted. A century earlier, William Penn, a prominent Quaker and namesake of Pennsylvania, was a catalyst for the changes that transformed these British colonies into an independent nation. Today, modern office towers exist side-by-side with the narrow cobblestone streets of Independence Historic National Park, which is home to historic buildings and sights, including the Liberty Bell, Franklin Court, and Independence Hall. To the south lies Society Hill, the city’s original residential area. Many of these eighteenth-century buildings have been handsomely restored. Similarly, Germantown in northwest Philadelphia, is another old residential section, first inhabited by Germans and the Dutch. To the west, along Schuylkill River, lies Fairmount Park, a vast belt of green containing numerous Federal-style mansions, as well as the Philadelphia Museum of Art and the Rodin Museum. Just south of that lies the museum district, including the Franklin Institute of Science Museum and the Academy of Natural Sciences.