Upper Iowa River Bridge
a.k.a. Hartley Bridge
Mays Prairie Rd. over Upper Iowa R., Dorchester, IAThis medium-span through truss carries a gravel-surfaced road over the Upper Iowa River southeast of Dorchester, in Union City Township. The road is presently a secondary one, but the crossing was once located on the main road between Dorchester and New Albin. The first permanent bridge was built here around 1870 by Allamakee County. Comprised of a two-span bowstring arch-truss, it had deteriorated to the point of replacement by the early 1910s. In 1913 the county removed the old bridge and solicited competitive proposals for its replacement. Although the project was relatively modest in scale, bids were received from 13 state and regional firms. The contract to build the new concrete substructure was awarded to New Hampton, Iowa, firm Chambers and Dobson for $2585.00. The Clinton Bridge and Iron Works were hired to fabricate and erect the rigid-connected Pratt truss for $3490.00. Using steel components rolled by the Illinois Steel Company, Clinton fabricated the truss and shipped it to Allamakee County. The Upper Iowa River Bridge was completed in July 1914. It has functioned in place since in unaltered condition.
When this bridge was let for bids in 1913, the Iowa State Highway Commission was just getting underway with its legislatively mandated program to standardize bridge design in the state. Although the highway commission delineated standards for pony trusses and smallscale concrete structures in 1913, it was not until the following year that truss designs were developed. This left counties such as Allamakee to depend - as they had for decades before - largely on the bridge companies themselves for both engineering and construction. The Upper Iowa River Bridge was built during this transitional period. Using a rigid connected Pratt through truss, it resembled the 1914 state standards in design but differed slightly in detail, indicative of its independent source. It is thus technologically significant as one of the last of the pre-ISHC trusses in the state. Of less momentous importance is the builder's plate on the bridge's portal. Consisting of a pierced plate with a crenelated top, it is the only one of its kind identified by the statewide bridge inventory.
Listed in National Register of Historic Places in 1998.
The National Register of Historic Places is the official list of the Nation’s historic places worthy of preservation. Authorized by the National Historic Preservation Act of 1966, the National Park Service’s National Register of Historic Places is part of a national program to coordinate and support public and private efforts to identify, evaluate, and protect America’s historic and archeological resources.