Hi Barton,
Nice pictures!
My guess is that the stonework held the original truss, which was replaced and the span shortened in 1930 to increase the load limit.
Regards,
Art S.
The Poteau River bridge is on the former St. Louis-San Francisco (Frisco) Arthur Subdivision between Fort Smith (AR) and Paris (TX). The line is now used by Kansas City Southern between Poteau (OK) and Fort Smith as their Fort Smith line.
The bridge has one short deck plate girder span on each end of the thru truss span. There are timber trestles off each end, with 16 timber bents on the east (north) end, and 56 bents on the west (south) end.
The through truss sits on concrete piers (listed as bents 18 and 19) with 1930 dates on them. The older cut-stone piers (bents 17 and 20) support the far ends of the deck plate girder spans.
Attached are a few pictures from November 2021.
I can say with with certainty this bridge is not on the Union Pacific. It was originally the frisco line and is now owned by Kansas city Southern, who still operates on this line to Fort Smith. This bridge is on the exact same line that Jenson Tunnel is on. This bridge being on the outskirts of Poteau, Jenson Tunnel at rock island/pocola through backbone mountain.
"My guess is that the stonework held the original truss, which was replaced and the span shortened in 1930 to increase the load limit."
That's my thoughts also and why the 1930 date is so important, but I haven't found any reports to confirm it yet. I'm still looking....