Old St. Mary's Church is on 4th St. between Locust and Spruce sts. Built in 1763 and enlarged in 1810, this was the second Roman Catholic church in Philadelphia. George Washington and John Adams are two of the many early American leaders who attended services here.
On July 4, 1779, the Continental Congress commemorated the Declaration of Independence, which marked the first public religious commemoration of the document. Another first came in 1810 when it was made the city's first cathedral. The cemetery dates to 1759.