- September 6, 1943 - 79 people are killed when a Pennsylvania Railroad train derails in Kensington.
- September 15, 1855 - Philadelphia City Council dedicates Fairmount Park to the public.
- September 22, 1734 - A large number of followers of the Schwenkfelder Church, a religious sect that follows the teachings of Kaspar Schwenkfeld von Ossig, arrive in Philadelphia.
- September 26, 1777 - American Revolutionary War: British forces, led by General Howe, march into Philadelphia.
