- The middle of the bridge, the part spanning the river, looks different than the two sides that do not span the river. Why would bridge engineer George Morison design the viaduct so that no posts or supports were in the water?
- What is the benefit of having a double track across the viaduct instead of a single track?
"Elevatin of Truss, From North, With Train - Chicago & Northwestern Railroad Viaduct, Spanning Des Moines River at Chicago & Northwestern Railroad tracks, Boone, Boone County, IA," Historic American Engineering Record. Courtesy of Library of Congress