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Additional Information: In comparing the non-original copy builder plaque on this bridge it has come to our attention that original King bowstring plaques list July 30 as the patent date, while this plaque lists July 3, likely an error.
This bridge is a King Bridge Company bowstring. Historicbridges.org completed an extensive photo-documentation of the McDowell Bridge, another King Bridge Company bowstring in Iowa. Visit the McDowell Bridge page to learn more about King bowstrings and see a more extensive photo-documentation of the many noteworthy details on a King bowstring truss.
The Hale Bridge was relocated and rehabilitated, and now resides in Wapsipinicon State Park in Anamosa . Be sure to visit the historic Cemetery Road Bridge, also part of the park.
The Hale Bridge is rare, not only as a bowstring truss bridge, but in addition as a multiple span bowstring, since the bridge contains three spans, two of those pony spans and one a through span. As such, the bridge is also the longest bowstring bridge in Iowa. The bridge was relocated and preserved in a park setting for non-motorized use. The relocation of the bridge spans was unusual not so much because they were moved all in one piece but because Chinook helicopters were used to lift and move them, representing a creative and unusual way to relocate truss spans. As a result of this relocation, the Hale Bridge gained brief national attention, since the History Channel featured the bridge relocation as part of a television program called Mega Movers.
The Hale Bridge has fair historic integrity overall, with the through truss span having relatively poor historic integrity compared to a number of the smaller King bowstrings remaining in Iowa. This assessment is due to several alterations on the through truss span. Two sway bracing beams on the through truss have been replaced and are not original. These replacement pieces contain numerous welded parts. This alteration appears to date from before the bridge's relocation and preservation project. In addition, two vertical members appear to have been replaced and similar to the sway bracing contain numerous welded parts. This alteration also appears to date to before the relocation and preservation work. The bridge apparently suffered repeated flood-related damage which is what resulted in these alterations, and perhaps some additional ones not observed. Finally, the bridge as a whole has historically insensitive cyclone fencing, apparently added as part of the relocation. It would have been nice to see one of the many alternatives to cyclone fencing that are much more attractive yet also meet demands for safety and accessibility present on this bridge, especially given the bridge's historic significance and newfound function as a historic landmark and centerpiece for the park it now serves.
That said, the pony truss superstructures appear to retain much better historic integrity than the through truss span. In addition, the bridge retains its extremely high degree of significance as a three-span example of a King bowstring. As a relocated bridge, the structure is also an attractive and functional crossing and attraction for a relatively large park. Overall this bridge represents an excellent and creative preservation solution and represents the diversity of alternatives to demolition and potential forms and methods of reuse that exist with historic truss bridges.
Bowstring truss bridges are sometimes called bowstring arch bridges because they have similarities to both structure types. Beginning with Squire Whipple's Whipple Arch Bridges, such as the Ehrmentraut Farm Bridge, the bowstring truss bridge is the bridge type that began a transition away from wood and stone and began to make metal a common bridge building material. It also began a period of experimentation until a good bridge form was developed, leading to a gradual standardization of bridge design. During this period, numerous bridge companies all experimented with metal, trying to design the best bridge. Each company had their own distinctive bowstring design, including unique and creative design details. These designs were often patented. Most bowstring truss bridges were built in the 1870s. Also during this time, cast iron was still used in addition to wrought iron for the construction of bridges, so many bowstrings built during this period include details such as connection assemblies that are made of cast iron. By the 1880s, bridge companies decided that the pin-connected Pratt truss was a better structure type, and construction of bowstring bridges sharply dropped after 1880. Because of the period in which Iowa was first being settled, a much larger number of bowstring truss bridges were built in the state than in other states. As a result, even today, Iowa has more historic bowstring truss bridges than any other state, although the number of bridges statewide is under 20, a very small number. However, a number of states do not have even a single historic bowstring truss within their borders. As such, while bowstring truss bridges are very few in number in Iowa, they are extremely rare on a national scale. It is imperative that each surviving bowstring in the county be preserved to protect this key period in bridge building history.
Historic American Engineering Record created a large and very informative historical overview and context for Iowa's bridges, and it is offered here by HistoricBridges.org in convenient PDF format for easy printing or offline viewing. The HAER source for the documents composing the PDF is here.
View Bowstring Arch Bridges of Iowa, An Online Book By Michael Finn (PDF)Michael Finn has composed a concise and detailed overview of Iowa's beautiful historic bowstring bridges. It has been made available for free by Iowa Department of Transportation.
View Historic American Engineering Record's Structural Analysis of Iron Bowstring Bridges (PDF)Historic American Engineering Record created a large and very informative structural analysis of how bowstring truss/arch bridges function. Everything from basic discussion of the engineering behind the bridges to advanced mathematical equations are available. The HAER source for the documents composing the PDF is here.
View Excerpts From Other HAER Documentation Describing the King Bridge Company's HistoryEach time HAER documents a bridge built by King Bridge Company, they often create a historical narrative for the history of King Bridge Company. HistoricBridges.org has searched through these narratives and offers here a convenient PDF version of two of the longer and more informative narratives.
View The First King Bridge Company Bowstring Patent (PDF)Zenas King first patented a bowstring design in 1866. Later, two more patents were issued. These later two patents are closer to the construction date of the Hale Bridge, and thus reflect more closely the design seen in the Hale Bridge. This is the first patent.
View The Second King Bridge Company Bowstring Patent (PDF)Zenas King first patented a bowstring design in 1866. Later, two more patents were issued. These later two patents are closer to the construction date of the Hale Bridge, and thus reflect more closely the design seen in the Hale Bridge. This is the second patent.
Information and Findings From Iowa's Historic Bridge InventoryDiscussion of Bridge
The bowstring arch-truss was the iron span of choice for Iowa counties in the late 1860s and 1870s. Marketed exclusively throughout the Midwest by such industry giants as the King Iron Bridge and Manufacturing Company and the Wrought Iron Bridge Company, these often-patented bridge configurations featured a wide range of span lengths, economical fabrication cost and relatively quick erection. The proliferation of the bowstring corresponded with the initial development of Iowa's road system; as a result, perhaps thousands of these prototypical iron spans were erected throughout the state. The bowstring had some rather severe structural flaws, however, relating primarily to lateral stability of the arches, and it was largely superseded by the pin-connected truss in the early 1880s. Despite this, some bowstrings were still erected in Iowa in the 1880s, although the number dwindled precipitously by the decade's end. Through subsequent attrition, almost all of Iowa's bowstrings have since been replace and demolished. Now less than twenty remain in place. Through its association with the King Iron Bridge and Manufacturing Company and owing to its multiplicity of spans, the Hale Bridge is both historically and technologically significant as one of the last remaining examples in the state of what was once a mainstay structural type [adapted from Hybben, Roise, and Fraser 1992]. Bridge Considered Historic By Survey: Yes |
This bridge is tagged with the following special condition(s): Reused
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