Photo taken by Fmiser in June 2012
License: Creative Commons Attribution-Share-Alike (CC BY-SA)
Thanks for the map link. It shows pretty much the same thing I already had - and that it appears possible to get to the bridge from the north.
Perhaps this map of the county roads will help you find a way to the bridge that is public property.
There is a "No Trespassing" sign on the road from the south. The sign is about 750 ft (230 m) from IL97. Looking at satellite images - after my visit - suggests it might be possible to get to the bridge from the north, and it appears the bridge may still have a deck. However, those No Tresspassing signs are hard to spot in the satellite photos.