Mystery Bridge Nr. 175: The Iron Road Bridge in Jackson County, Iowa

Photos taken by Troy Knox of Bridging the Driftless

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The next bridge in the Mystery Bridge series is the second of two installments of the bridges in Jackson County, in eastern Iowa. Yet one can look at it as two bridges, because each one has the same problem: looking for the bridge builder. And judging by the identical length these structures have, it may appear that they came from a multiple span structure that had been cut up into spans before shipping them.

After looking at the now extant Caven Bridge, we have this bridge at Iron Bridge Road. It spans the Maquoketa River on the road bearing the bridge’s name, approximately 8-10 miles NW of Spragueville. It’s at the junction of Miller Access Road. The bridge is a Pennsylvania through truss bridge with riveted connections, I-beams and M-frame portal bracings. It has a total length of 420 feet but the truss bridge’s length is 250 feet, thus making it the longest single-span Pennsylvania through truss bridge built in the state. It’s even longer than the Traer Street Bridge in Greene (in Butler County), which was replaced in 1981 after 79 years in service.

According to records in bridgehunter.com, the bridge was built by the Iowa State Highway Commission, which today is the Iowa Department of Transportation. It was established in 1904 and was one of the first highway institutions to have made firsts in the field of transportation, which included traffic signs, like the No Passing Zone sign, as well as paved highways made of tar and later concrete, and finally bridge designs. Yet despite the claims that the State Highway Commission was responsible for building the bridge, it can only be credited for making the design of the standardized truss bridges, which were introduced from 1910 on. What is missing is having the bridge builder who is in charge of constructing the bridge as well as the company that fabricated and transported the steel from the steel mills. It is a foregone conclusion that a highway agency would not have a bridge building firm with steel mills on their lots unless the agency had vast amounts of land to build the steel mills. That would have taken up half of Ames, where the highway agency is still located today.

This leads us to this question: If the highway designed the truss bridge, like the one on Iron Road, where did the steel come from, and who oversaw the construction of the bridge?

These are the two key questions not only for the Iron Bridge here but also its twin bridge, the Damon Bridge, spanning the same river but on 435th Avenue (County Hwy. Z 34), six miles north of Preston. The bridge has the exact same form as the Iron Bridge but was built six years later, in 1956. If you have any information on the two bridges and their predecessors, feel free to comment in the Chronicles directly online, but also in bridgehunter.com under their respective pages.

Your bridge matters! Best of luck in the research. 🙂

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