Center City includes the central business district and central neighborhoods of Philadelphia, Pennsylvania, United States. It comprises the area that made up the City of Philadelphia prior to the Act of Consolidation, 1854, which extended the city borders to be coterminous with Philadelphia County. The area has grown to the second-most densely populated downtown area in the United States, with an estimated 202,000 residents in 2020 and a population density of 26,234 per square mile.