Pennsylvania Truss Bridges: The longest of the truss bridge types that were used for America’s transportation system, but the rarely used. Or was it? This is the question that many researchers have been asking for many years, as many of them are compiling materials for bridge books, for even though statewide surveys were carried out at the earliest 20 years ago, questions about the credibility of the information has come up, which includes finding out how useful these bridges actually were, let alone how many of them were actually built in comparison to what was found in the research. Part of it has to do with the number of post cards and old pictures that people have found recently of old bridges that carry the signature design.
Developed and patented in 1875 for the Pennsylvania Railroad, the Pennsylvania Truss Bridge is similar to the Parker Bridge, because of its polygonal top chord, yet it has subdivided diagonal beams supporting the main diagonal beams. Furthermore, as seen in the photo of the now extant Orr Bridge in Harrison County (Iowa), diagonal beams cross not one but two panels at the center of the span. Pennsylvania trusses were used not only as single span crossings but also for wider river crossings as multiple spans, including those along the Mississippi and Missouri Rivers, many of which have long since disappeared. Reason for that is the fact that these bridges can range from 130 to 600 feet long, some even longer. While these bridges were used for that purpose, the danger was that of the pressure applied to the roadway, creating tension to the diagonal beams and upper chord, resulting in the failure of even one of the subdivided beams, and as a consequence, the failure of the entire structure. That is the reason why they were used rarely. Or were they?
This is where we look at the state of Iowa as the subject of debate. 20-25 years ago, a survey was conducted on Iowa’s truss bridges revealed that even though some Pennsylvania truss bridges were used for large crossings, like the Mississippi River crossings at Clinton and Muscatine, as well as the longest single-span crossing in the state at Greene (at 249 feet), the number of these bridges were rarely used in bridge building between 1880 and 1920. Seven bridges listed in the survey were examples of this bridge type, including the Thunder and Old Rusty Bridges in Spencer, the Bridgeport Bridge near Keokuk, one span of the multi-span Boone Bridge, the Rubio in Washington County, and the Berkheimer Bridge west of Humboldt, and the Orr Bridge. The Orr and Rubio Bridges have long since been removed. The Berkheimer Bridge currently holds the title as the longest bridge in the state, despite being closed to traffic between 2001 and 2005 for rehabilitation.
Yet two problems have come up that have the potential to refute the claim of its rare use on the state’s roads. The first one is the fact that at least three bridges surveyed have Pennsylvania truss types but have a flat lateral top chord, thus making them Camelback Pennsylvania trusses. This includes the Gochenour Bridge in Harrison County, and two bridges spanning the Cedar River in Mitchell County: the Otranto Bridge and the Deering Ford Bridge, the latter of which was replaced 15 years ago; the former is now privately owned and can be seen from its replacement bridge.
The other one, which is perhaps the biggest of the problems supporting the claim is the number of Pennsylvania truss bridges that had existed prior to 1970. Even though they were demolished before a HABS-HAER survey was conducted on the Greene Bridge in 1979, two years prior to its demolition and replacement, recent discoveries by a pair of pontists residing in Iowa reveal that more of these that existed, thus putting the historic survey’s claim in doubt. This is not only applicable to multiple-span bridges, but also and especially to the single-span bridges. Some examples supporting the claim include another Skunk River crossing at Brighton, east of the Rubio Bridge, the Second Street Bridge in Independence, The Lincoln Highway Bridge over the Wapsipinicon River in Clinton County, a Big Sioux River crossing near Canton, South Dakota, Ripley’s Bridge in Floyd County, and a Little Sioux River crossing at Sioux Rapids in Buena Vista County. With as many bridges of this kind along the Little Sioux River, one can even stretch the claim that the river may be the river with the highest amount of Pennsylvania trusses.
In addition to the argument supporting more Pennsylvania trusses built in Iowa, it is possible that other bridge companies may have contributed in its construction of Pennsylvania truss bridges. While it is true that the Clinton Bridge and Iron Works Company constructed the majority of these truss bridges, including the ones in Greene, Spencer, and west of Humboldt, other bridge companies, such as the Iowa Bridge Company of Des Moines, Chicago Bridge and Iron Works, and even the Canton Bridge Company in Ohio took a piece of the bridge building pie as well. If one adds the Gochenour and Orr Bridges to the list of unknown bridge builders, as they were imported into Iowa in the 1950s, then one can claim that other bridge companies tried to keep Clinton from monopolizing the bridge building industry in Iowa by building their own Pennsylvania truss bridges, even though surveys confirmed that Iowa BC and Chicago B and IWC constructed them.
The last one is the fact that Pennsylvania truss bridges were built well into the 1960s, for one can find two of these structures in Jackson County, spanning the Maquoketa River: one at Iron Bridge Road, and one on County Highway Z-34. It is possible that other bridges of that type built during that period can be found in Iowa as well, for these bridges were part of the standardized truss bridges, featuring riveted connections, that were introduced on Iowa’s highways beginning in 1914, although they were not used as often as the other truss bridge counterparts, such as the Pratt, Warren and Parker truss bridges.
All these claims lead to the following questions for the forum:
1. How many Pennsylvania truss bridges were actually built in Iowa between 1880 and 1960?
2. What other single span Pennsylvania truss bridges existed prior to 1970, besides the ones mentioned in the article? When and where were they built and who was the bridge builder?
3. Why were Pennsylvania truss bridges built beyond 1920 instead of the other truss types?
There are four ways to answer this question: One is directly through the social networking sites of Facebook and LinkedIn under the Bridgehunter’s Chronicles; the other is by leaving a reply in the comment section; the third option is via e-mail, and the fourth option is through the Historic Bridge Weekend, which takes place August 9-11 (please see the info here). There you can leave the info and photos in the Info and Photo Box, provided at the evening events or you can talk to the author directly, as he will be directing the conference in its entirety. The information will be used for the book project on Iowa’s Truss Bridges, which is ongoing as information is being collected as of present.
Pennsylvania truss bridges were a useful commodity on America’s roads, and to a certain degree, they still are today. Yet it remains questionable how many were really built and why they disappeared so rapidly, even though their lifespan was the same as any other truss bridge built between 1860 and the present- 70-120 years, pending on how they were used and how they were and still are maintained today.
Special thanks to Hank Zaletel and Luke Harden for digging out and submitting the photos, as well as allowing me to use the photos for this article.