The Bethlehem Steel archives are in Delaware at the Hagley. There may be information there about the C&BL including contract info on the bridges. It's possible there is a plate to be viewed but if it's easy to get to it may have been "collected".
I guess the only way to find out who built the bridges is to look for any manufacturers stamps in the metal or a plaque,Clark.Wouldn't that be the right thing to do if you're not tresspassing?
The 1904 and 1907 Johnstown 15' shows no RR and notes the Old Portage Tunnel with an abandoned grade. In 1964 the railroad is the C&BL crossing the river to a series of loops and spurs and a "Slag Dump".
These bridges were probably built for Bethlehem Steel ca. 1924.
Welcome George, Kudos to Josh for field visit and Clark for RR!
Dana and Kay,thanks for posting this bridge on Bridgehunters.From what it looks like,this bridge along with the truss bridge were part of a quarry of some sort that looks abandoned.Shouldn't be hard finding information on which railroad abandoned this bridge or if they're privately owned.
Thanks,Clark.Always good to know where information might be.