I found the site of this bridge. It would appear that a new bridge was built on a slightly different alignment, and then the old bridge was removed.
Your right Matthew.....I looked at these photos on the HAER sites and they are for another bridge that also spanned the Pecatonica River on Winneshiek Road near Freeport. Apparently that bridge is now gone, while the Van Buren Ave. bridge remains.
I've noticed that the Whipple truss bridge shown in the first photograph is not the same bridge as the one shown in the rest of the photos or the one referenced by the HAER link (the other is a Pratt truss).