+++ Location Based Wherigo +++
When you arrive at the posted coordinates you will see a posted sign with a ton of history lessons on Bridgeport Township and the bridge. You must answer the questions from the posted sign. All answers can be found here. But you must look for them here. When all ten or so questions are answered, it will take you to the next waypoint. There's about three more points you must go to. You do not not have to do anything at the others. Enjoy your walk along the trail!
Update 3/27/2024:
Option 2: Take of Pic of you with the posted history about the town and bridge here. You may also take pictures on the bridge and will count as a find.
I highly recommend just walking the rail trail though. It's pretty short.