I have seen various dates for construction given but I can only say for sure that the bridges were built in the early 1900's. I would say somewhere between 1910 & 1920 would be good. The NKP Bridge was raised to the upright position in 1988. There are shots of trains crossing both of the bridges in the books: Niagara By Rail by Pete Jehrio, Nickle Plate Color Photography Bellview to Buffalo by Morning Sun Books, and there's an awesome shot of an ore boat passing through the draws in the ( Feb ?? ) 1976 Trains Magazine article on Buffalo by Devon Lawton along with N&W trains on the bridge. Back a few years ago before the entire world went paranoid, I used to sit on the torn up ROW by the NKP bridge and watch trains or boats from that location. The bridge itself seems to move around a lot when a breeze kicks up since it makes all sorts or creeking, moaning, and banging noises in the wind. Not sure if it's supposed to move that much, but it seemed to me to be rolling back a little, and then falling down with a slight bump onto the steel columns that they welded up there to keep it raised. That location is a great study in presence Vs. absense, lots of industrial ghosts hanging around from days long since past, but still a lot of activity if you show up at the right time.
If you look closely the NKP bridge is a totally different design. The bridge raises & lowers on a toothed wheel instead of the CP Draw design of a counterweight ballanced by a rack & pinion. The NKP bridge remains "stiff" as it raises and lowers as the structure does not have any moving parts other than the gearing & motor to move the roller assemblies. CP Draw is a more typical (for Buffalo) bascule bridge in that the entire bridge structure collapses on itself when it goes up. There was only one other rolling bridge like the NKP in town and that was the old South Michigan St. Bridge that was removed after the Skyway was built. That NKP bridge really is a relic. All the other moveable RR bridges in town (7 of them total) were either swing or bascule style like CP Draw.
I would hazzard a guess that CSX will have to open them pretty soon to allow for icebreaking operations on the Buffalo River. This winter has been cold, and the crick is pretty froze up right now. They will probably be sending either the firetug Cotter, or a Coast Guard Ice Breaker up there one of these days to keep South Buffalo from flooding once we get a thaw.
-B in B