http://www.railpictures.net/viewphoto.php?id=158898&nseq=305 The plaque shape is reminiscent of a Lassig Bridge & Iron plaque, but based on the time in which this bridge was built, based on the build date of an overpass on the approach, would have put it being built After the takeover of Lassig by the American Bridge Company, who used Lassig shaped plaques on some of their bridges, as seen here: http://www.youtube.com/watch?v=WL67AiM295M&feature=relmfu
Based on that I am listing the build date as 1900 and the builders as the Lassig Branch of the American Bridge Company
Well, I found out this bridge has a plaque, but there is an issue: It's located on the span over the middle of the river, and the other one I saw in an image was severely broken: http://www.railpictures.net/viewphoto.php?id=158898&nseq=305
This photo (I took in 2006) is in the public domain and shows the bridge quite well, along with a pair of heavy Chinese QJ steam locomotives. Railroad bridges always seem to look better under steam.
I don't know any of the exact dates, nor what the original bridge was. I've been assured that there used to be a different bridge on these piers, the old people who have told me this can't remember what exact type, but it was not just a single deck girder.
If you know the history and year of the piers you should add it to the bridge description.
Looks like those piers are from a much older bridge.