On the Illinois historical aerial photography website I found a late 1920s aerial view of the railroad/highway bridge at Fort Madison. I'd say this photo was taken not too long after the current bridge was completed. The original 1880s swing bridge is shown too, though the swing span and western approach have already been removed. This photo clearly shows that the current 1920s bridge was built upstream from the original 1880s bridge it replaced.
The photo is also upside down, with south up and north down.