As far as I know, all Rock Island railroad tracks in Missouri have been unused but not abandoned.
I checked the Bird's Eye setting for the MSN Live Search Map at this location. The tracks have been taken up but the bridge appears to be in place. This would make a good field trip.
The entire old RI line is being converted into the MoRIT, Missouri Rock Island Rail Trail. Although I did not make it this bridge, the line appears to be cleared and and grubbed with all rail removed.