This bridge is also known as the Riverton Bridge, the Union Railroad Bridge and the Mckeesport Connecting Bridge. pghbridges has the date of 1890, whereas Bridge Hunter claims 1891. (Update: Brian G's comment indicates the builders plaque has 1891, so I changed the date in the title.)
I'm not researching every big railroad bridge I see. For example, I didn't do the Arthur Kill Bridge until I learned it has the longest lift span in the USA. But this truss bridge is special for a couple of reasons. One is that it was converted to a trail bridge in 2007. [Wikipedia] (Bridge Hunter implies it became part of the trail in 2008.) It is part of a trail system that connects Pittsburgh with Washington D.C. The second reason is that it is yet another RR bridge over the Monongahela River that connects two steel making facilities. In this case it connects the US Steel Duquesne Works with its Dorothy blast furnace to the National Tube Works in McKeesport. It also connected the Pennsy on the south (McKeesport) bank with the B&O on the north bank. [pghbridges]
|Joseph Flickr, License Creative Commons Attribution-NonCommercial-ShareAlike (CC BY-NC-SA)|
McKeesport Connecting Railroad Bridge
This photo shows the 1890s technologies of cut stone piers and pin-connected tie bars.
|A Paul Wiegman Photo via SteelValleyTrail via Bridge Hunter, License: Creative Commons Attribution-Share-Alike (CC BY-SA)|
The bridge, now part of the trail, provided the rail connection between the National Tube Works at McKeesport and the USS Dorothy Six blast furnace of the Duquesne Works
|Steven J Raith posted|
Union Railroad crossing the McKeesport Transfer Bridge on June 28, 1997. Originally built by the PRR, the Union acquired trackage right over the bridge in 1965 and outright purchased it in 1976. US Steel donated the bridge to the local rails to trails and today you can walk (or bike) over it.
Ian Bowling Steven J Raith do you remember when the last train ran across this bridge? I remember in the early 2000’s that me and my dad saw one going across it at night. That was the last and only time I seen one go across this bridge.
Steven J Raith I want to say around 2006 or 2007? not 100% sure.
Ian Bowling Steven J Raith okay that’s about the time I can remember seeing it. I would’ve loved to catch it in the daytime. Awesome photo!!
[If Steven's dates are correct, then the bridge was converted to trail use within a year or two of the last train running on it.]
|M'ke Helbing shared|
Former Pittsburgh and Lake Erie Railroad bridge over the Monongahela River from Homestead toward Carrie Furnace PA
Rail bridge on Great Allegheny Passage over Monongahela River, Duquesne PA
Mike Helbing shared
Great Allegheny Passage across the Monongahela River into McKeesport PA.
M'ke Helbing shared
|J.B. Rail Photo shared GT Rail Fan Productions|
8/26/2021 - CSX P001 strolls through McKeesport PA rounding through the classic Bridge in town over the Youghiogheny River! This is one my favorite photos of all time.
[I didn't look at the video, the photo does it for me.]
YouTube Video Link of the CSX OCS Chase:
InterestingPennsylvania has more photos from and of the bridge. It appears the bridge owners think that it will take rust a long time to reduce the strength of a railroad bridge to be less than that of a trail bridge because the bridge looks rather rusty.