Line was abandoned from DeWitt to Eldridge in 1931 based on the book I just added to the sources section. Based on the lightweight construction, it was relocated here. Something that, based on the many relocations John Marvig's uncovered, comes as no shock.
It is, as the only other railroad bridge in the general vicinity was the Rock Island/BCRN bridge at McCausland, but that line was heading northeasterly towards Clinton.
Also it (And all other bridges on that line.) were gone by 1937, as they don't appear in aerial views from that year.
This may be the bridge Henry was commenting on.
There also appears to be a girder bridge a bit north on what is still somewhat visible as the old ROW.
Or is it a privately built bridge?
41.767713, -90.575397
arrow on map should be 1/2 inch north on the original river