Historic Thomas Mill Bridge is the last remaining covered bridge within the city limits of Philadelphia. You will find it along Forbidden Drive, near mile post 1, about a half mile below the parking lots at Bell's Mill.
I'm having difficulty finding a precise history of the bridge, but it most likely dates to the middle of the 1800's. The structure was restored in 1938 by the WPA, and in 1999 by the City of Philadelphia.
These photos were taken late Friday Morning.