There have been two structures with the name, although not at the same time. The western bridge was opened in 1864 and was designed by Joseph Cubitt. It was too weak to support modern trains and all that remains are a series of decorative columns crossing the Thames.
The eastern bridge was originally called St Paul's Railway Bridge and opened in 1886. It was designed by John Wolfe-Barry and H M Brunel and is made of wrought iron. When St Paul's railway station changed its name to Blackfriars in 1937 the bridge changed its name as well.