The two approach bridges are nearly identical using concrete girders and a concrete deck. The only real differences are that the Wisconsin Street Bridge is slightly longer, and it has a bit of a slant, while the Iowa Street Bridge is just slightly shorter but is built relatively level.
In the photo above, the Iowa Street Bridge is in the foreground, the Wisconsin Street Bridge is behind the Iowa Street Bridge, and the Blackhawk Street Bridge is visible in the background. This photo was taken while standing on the Saint Feriole Island railroad bridge.