Hugh Foundit: A fellow geocacher alerted me that the ammo box is gone. The park district was doing maintenance on the bridge and may have removed the ammo box.
For those of you who didn't find it, the trick to this one was that both WPs were fake bolts in the fence posts and each bolt had the same coordinates. The coordinates took you back to the starting point where the final was an ammo box located under the SW side of the south end of the bridge. You were literally standing on the ammo box at the second WP. It was meant to be a head scratcher - either it clicked immediately or it stumped you.
Thanks to all who found it and thanks for all the favorite points.