The Roman Catholic Archdiocese of Philadelphia is an ecclesiastical territory or diocese of the Roman Catholic Church in southeastern Pennsylvania, in the United States. It covers the City and County of Philadelphia as well as Bucks, Chester, Delaware, and Montgomery counties. The diocese was erected by Pope Pius VII on April 8, 1808, from territories of the Archdiocese of Baltimore. Originally the diocese included all of Pennsylvania, Delaware, and seven counties and parts of three counties in New Jersey. The diocese was raised to the dignity of a metropolitan archdiocese on February 12, 1875. The seat of the archbishop is the Cathedral-Basilica of Ss.