Distant View, Showing Bridge In Context With Agricultural (Pastures And Cornfields) Setting; Looking Southeast
Photo by J. Ceronie, photographer, Bennett, Muessig & Associates, Ltd., Iowa City, IA, May 1983, for HAER
The Eureka Bridge is an example of one of the most common bridge types in late Nineteenth-Century Iowa. It is what engineers and historians call a "bowstring" bridge, referring to its shape in profile and its fundamental structural action. This form of wrought-iron bridge was widely used for wagon road crossings of both small streams and, in multiple-span arrangements, major rivers. It was built from the late 1860s until the early 1880s. Bowstrings, being of relatively light construction, were rarely, if ever, used for railroad purposes.
The name "Eureka" comes from the proprietary name given to the type by the manufacturer, initially a small firm in Wisconsin. The history of the Eureka type in general and of this particular bridge, apparently the only known surviving example, is not easy to discover. But, the bridge is there; despite gaps in the paper trail we can get a fair idea of the entrepreneurial dynamism that found such a focus in technological innovation during the last century. As Eric DeLony puts it, "This bridge is a classic example of the prefabricated iron-truss bridge patented and manufactured by entrepreneurs for local farm-to-market road use."
Considering the surviving bridge itself, the artifact, we are faced with two questions. First, is this structure identifiable with the bridge patented in 1871 by Oliver H. Perry and William H. Allen? And, second, what is the provenance of this particular example?
A beginning difficulty is that the Perry and Allen patent was issued on Tuesday, October 24, 1871, while cast into one of the parts (numbered"5"; there are 17 examples on the bridge) is: "PATD OCT 1872." A check of the patent office Gazette reveals no patents to Perry and Allen on Tuesday, October 22, 1872, the nearest patent issue date appropriate to the cast year. [Editor's note: Patents were issued on Tuesdays.] We must therefore assume that the pattern maker made a mistake and placed a "2" instead of a "1" in the year date on the pattern. The lettering style was a common one used in foundries, and Beloit, Wisconsin, home of the patentees, had a large foundry. Thus 1872, while not the true patent date, probably represents the year in which the pattern was fabricated and the iron cast.
A second difficulty is that the existing bridge apparently does not actually demonstrate the use of the patent granted. The claim of Perry and Allen was four "coupling clamping-seats...arranged to receive and support the adjacent ends of the arched rods [upper chord]...and form a connection for the arched-rods [web members] thus dispensing with separate or tubular couplings for this purpose...We are left with a bridge that, as built, is not even covered by the patent which identifies it. Yet there is little real doubt that this is a bridge whose design has its origin in the Perry and Allen patent.
The other important question concerns the origin and history of this particular bridge. A search of the Winneshiek County Bridge Expense Journal, 1872-1899, yielded no record whatever of any Eureka Bridge erected in Bloomfield Township (where the bridge was last in service) or elsewhere. Since the journal began in the earliest possible year that the bridge was fabricated, this means that the county did not pay for it. This does not mean, however, close off close off all possible explanations. In Iowa the township government had control over the roads until about 1900. Therefore, a township might have contracted for a small bridge on its own, especially if county aid was not available. An example is recorded in 1871 in the Winneshiek County Auditor's Bridge Calendar where three requests by townships for county bridge funds were "Refused, Apr 44, 1871, Being under 30' span." (The Eureka Bridge has a span of 28'* 8 1/2".)
...by 1876 he [Allen] had apparently sold the design to the Eureka Bridge & Iron Co. of Chicago...
We are left with the possibilities that the bridge was initially used at or near Ridgeway, then sold to Bloomfield Township, or that it was always somewhere in Bloomfield Township, or that is was always somewhere in Bloomfield Township but moved within the township at least once.
No other Perry-Allen patent "Eureka" bridges are known in Iowa, although an old "freak bridge" of bowstring form, built of bars with cast-iron joint fittings, was reported in the engineering press some sixty years ago. Whether this structure was one of those of which Allen "introduced a number" in Iowa is doubtful. But the Eureka Bridge and all the others like it, although hardly examples of expert bridge design, demonstrated both the entrepreneurial ferment and the wide spread of the industrial revolution which were characteristic of Nineteenth-Century America.
[Editor's Note: The complete essay can be found in the HAER collection in the Library of Congress website. Mr. Hippen's description of the "Eureka" bridge explains how some bridges in Iowa, such as the Raccoon River Lincoln Highway Bridge in Green County, Iowa, have the name "Eureka Bridge" for no obvious reason.]
"This document was prepared as part of the Iowa Historic Bridges Recording Project performed durng the Summer of 1995 by the Historic American Engineering Record (HAER). The project was sponsored by the Iowa Department of Transportation (IDOT)."
Historian: James C. Hippen, HAER 1996