The mission of the Historic American Engineering Record (HAER) is to document historically significant engineering, industrial, and maritime sites in the United States. HAER and its sister HABS (the Historic American Buildings Survey) are administered by the National Parks Service, U.S. Dept. of the Interior. A major part of HAER's efforts go into historic bridge surveys for key states. The project that I was involved with was the Iowa Historic Bridges Recording Project which was performed in the summer of 1995. The project was under the direction of the Chief of HAER, Eric Delony. If you have an interest in historic bridges I recommend his book: Landmark American Bridges
Fremont Mill Bridge (Detail) Center Junction, Iowa, 1873
This unique bridge is an example of a bridge type called the "Bowstring Arch" that was popular in the 1860s and 1870s. The picture shows the upper chord (which makes up the arch itself). It is built-up from flat iron plates joined by a web of hollow crossed rods, fabricated from extra heavy gas pipe. The bridge was designed by Joseph Davenport who is the person that built the first cow-catcher (the plow-like gizmo attached to the front of a railroad locomotive to push cows and other debris from the tracks).
If you would like a set of detailed HAER drawings for this bridge, you can download it from the Library of Congress.
The state of Kansas has numerous striking examples of the "rainbow" bridge design of James B. Marsh. This unique design used a complex steel skeleton encased in concrete. The deck is suspended from the concrete/steel arches. Marsh built hundreds of these bridges in the 1910s - 1930s mostly throughout the Midwest. These photos were taken by Richard With who is a computer programmer and lover of Marsh arches. He is a member of the Kansas Historic Route 66 Association
