Not the oldest, though. There are still a few systems running 1945-era PCC trolleys -- San Francisco, Philadelphia, and a spur line in Boston (Ashmont-Mattapan

Not the oldest, though. There are still a few systems running 1945-era PCC trolleys -- San Francisco, Philadelphia, and a spur line in Boston (Ashmont-Mattapan), though a lot of those have been subject to pretty dramatic overhauls. For heavier rail, the MBTA Red Line still has cars in service (the 1500 series) that were built in 1969-1970, and BART just very recently retired their original cars which entered service in 1972.