The pin connected bridge is highly decorative. It was a typical style by the Keystone Bridge Company, founded by Andrew Carnegie, the steel magnate.
This span is famous, and rightfully so, is on the National Register of Historic Places.
The span was relocated to Bergfeld pond, a park in an industrial area to the west of Dubuque.
The bridge is currently a fishing pier/observation deck, and wonderfully preserved.
These spans were built for an approach to the crossing of the Mississippi River in Dubuque by Illinois Central Railroad. These spans were filled and sold at various times. This one was sold to Dubuque County in 1890, and may have been the last one built.
The photo above is a basic elevation.