The Mowersville Road Bridge is a single span cast and wrought iron Pratt pony truss bridge which has a cast iron for compression members and wrought iron for tension members. The bridge contains eight panels which are unusual because they are not all the same length. In 1921, the bottom chord, flooring system, and lower portion of the vertical members were all encased in concrete and a center pier was added, which means that the truss no longer functions as a truss and the bridge instead functions as a two span concrete slab. Deterioration of the concrete reveals that today the original bottom chord remains in place as do the bottom chord connections so although this concrete has hidden original material and altered design of the bridge, the original parts of the bridge do remain in place.
The Pennsylvania Historic Bridge Inventory lists the bridge as eligible for listing in the National Register of Historic Places, and further lists the bridge as being nationally significant. This accurate assessment of the bridge is because of its use of cast iron for compression members, which makes it one of the rarest bridge types in existence. In the United States, cast iron was only used in bridge construction for a few decades in the 19th century, in the early years of metal bridge construction, with most examples dating from approximately 1850 to 1880. Nearly all surviving examples of metal bridges from this period have been demolished, making surviving examples far more rare and significant than other bridge types such as covered bridges. Further, like most cast iron truss bridges, the Mowersville Road Bridge displays unique non-standard member and connection designs that not only display the spirit of experimentation that accompanied this period of history, but also mean that the bridge may be unique with no other similar bridge remaining in existence. Although the bottom portion of the bridge has been encased in concrete, a limited number of vertical members have been replaced, and some bolted and welded additions are present, the bridge retains enough original materials and still conveys its original design so as to retain a national level of significance and rarity that makes the bridge deserving of the highest level of preservation priority.
Historic American Engineering Record documented this bridge with measured drawings, photos, and a narrative. However, the narrative has not been released to the public on the website, and so its contents are currently unknown. The overview description and descriptions on the drawings claim that this bridge was built in 1896 by prolific regional builders Nelson and Buchanan of Chambersburg, PA. Nelson and Buchanan, who were most often seen acting as agents for the Pittsburgh Bridge Company, generally followed highly standardized truss bridge designs that resulted in traditionally composed bridges made of wrought iron or steel. There is no other bridge associated with Nelson and Buchanan that has the design of the Mowersville Road Bridge. Further, in 1896, the use of cast iron for any part of a truss bridge, let alone primary structural members and chords had been obsolete for over 10 years, rapidly dying out by 1880. Indeed by 1896 even wrought iron was rapidly becoming obsolete as steel became the preferred material in metal bridge construction. The differing panel sizes in the truss also goes against period thinking in 1896. Therefore, without seeing the supporting HAER documentation it is a bit hard to believe that the physical bridge seen today was built in 1896 by Nelson and Buchanan. The bridge stylistically dates to ca. 1870. Cast iron bridges like this were often built by small foundries, not always by the larger bridge companies who came to dominate the late 19th Century scene starting in the 1870s. If this 1896 date and Nelson and Buchanan firm were involved, it seems more likely that they may have reused an old bridge be relocating it to Mowersville Road at that date, or perhaps they made repairs to the bridge.
Pennsylvania's Historic Bridge Inventory either was unaware of the HAER documentation or they didn't believe it either, since it lists the builder as unknown and the construction date as ca. 1870.
Until HistoricBridges.org sees the complete HAER documentation and explanation for the 1896 date, the bridge is being listed with an unknown construction date and builder.
On August 2012, it was reported that Franklin County demolished this bridge. This demolition rates in the top five worst demolitions among bridges covered by HistoricBridges.org since the website began in 2003, when taking into consideration both the significance of the bridge and the feasibility of avoiding demolition. The demolition means that a unique, one-of-a-kind bridge has been reduced to scrap metal. There are no other known bridges in the country that use the specific castings that were used on this bridge. The decision by Franklin County to demolish the bridge shows a complete disregard for the local community as well as a lack of common sense. Demolishing this bridge was unnecessary and a waste of taxpayer dollars. Consider the following points:
The bridge was demolished by Franklin County despite the fact that the bridge was nationally significant and represented one of the rarest types of bridges in the country, a cast iron truss.
The bridge was demolished by Franklin County despite widespread support for leaving the bridge standing among the local community.
The bridge was demolished by Franklin County despite the fact that it could have been dismantled and placed into storage indefinitely for future preservation, a storage that costs nothing if the parts are stored on government property.
The bridge was demolished by Franklin County despite the fact that it could have been closed to traffic and left standing either for pedestrians or closed to all traffic.
The bridge was demolished by Franklin County despite the fact that no replacement bridge is needed here. The ENTIRE detour length to drive from one end of the bridge to the other without crossing the bridge is a mere three quarters of a mile! This detour uses an unrestricted state highway crossing that can handle trucks and emergency vehicles.
The bridge was demolished by Franklin County despite the fact that Franklin County has preserved the Red Covered Bridge, a much more common type of historic bridge, representing the most common type of covered bridge.
The fact that Franklin County has preserved a historic covered bridge, yet refused to even discuss leaving this bridge standing closed to traffic is clear evidence of the wrongful bias present in the United States. HistoricBridges.org is not saying that the covered bridges should not be preserved. However, if the covered bridges are all preserved, than other historic bridge types of equal or greater significant (and with equal or greater feasibility of preservation), such as the Mowersville Road Bridge, need to be preserved as well, if for no other reason than in the interest of being fair. However time and time again, any historic bridge that has committed the crime of not being covered by wood is instead sent to the dumpster. This is why HistoricBridges.org does not feature covered bridges among its listings. It is time to focus the spotlight on other bridge types. It needs to be realized that bridges like the Mowersville Road Bridge are just as valuable if not more valuable than a covered bridge.
That Franklin County would demolish such a rare bridge that would have been so easy to simply leave standing and not demolish raises grave concerns about other county-owned historic bridges in Franklin County. These bridges do not stand a chance unless someone can convince Franklin County that historic bridges are more than cockroaches that need to be exterminated as quickly as possible at any cost.
Obviously one of the first things that comes to the mind of the historian who visits this bridge is that it would be interesting to remove the concrete from this bridge and restore the iron trusses to their original condition and make the bridge able to function as a truss again. There are however some issues that would have to be resolved to make this happen. The cast iron has cracked and broken in a few places, the worst issue being a crack that appears to have completely severed the southeast end post. The southwest endpost is also missing a portion of the beam which has broken away. Some of the diagonal members are no longer properly bolted to the top chord and have been welded. Removal of concrete would have to be done very carefully so as to maintain the integrity of the trusses. These issues could be resolved as part of a comprehensive restoration undertaken by firms with experience with historic bridge restoration.
At the same time, it seems appropriate to consider a preservation solution that retains the concrete encasement and pier, something that might be less costly, and also considers the perspective that even the alteration of concrete encasement, dating to 1921, could be considered to have at least some level of historic significance as an example of the odd ways in which local governments extended the service life of bridges. Extensive spalling was noted at the ends of the pier, and the bottom of the concrete slab has delaminated to the bottom chord and deck stringers of the truss in a few areas. However outside of these areas, initial soundings of the concrete suggest the concrete remains solid in most areas. An asphalt overlay on top of the concrete has deteriorated not only at the edges but also at the center where unusually high horse traffic on this bridge has worn away the asphalt. Unless they are perfectly sealed and watertight, asphalt overlays can be extremely detrimental to concrete decks since they tend to trap moisture in the concrete leading to deterioration. The asphalt overlay could be removed and either left off completely, or replaced with a waterproof overlay. Another issue that could be beneficial to the bridge in this preservation solution would be to adjust rip rap in the waterway so as to direct water flow in a way that it does not create a scour condition at the pier.
Franklin County, who owns this bridge, has expressed a desire to no longer have a bridge at this location and has proposed demolishing this nationally significant historic bridge. The demolition of a bridge with this level of rarity and significance would be nothing short of devastating to this nation's transportation heritage. Further, local residents have expressed an interest in having the bridge remain in place for non-motorized use. Franklin County and local residents are currently discussing the possibility of transferring ownership of the bridge to these local residents who would take responsibility for the operation of the bridge as a non-motorized crossing. The optimal solution would be for Franklin County to realize what a treasure this bridge is and to continue ownership of the bridge, convert it for non-motorized use, and perhaps provide basic maintenance services for the bridge, while also in the future perhaps seeking grants such as a Transportation Enhancement grant to undertake a complete restoration of the bridge. However, if Franklin County truly does not want to continue to own this historic bridge, HistoricBridges.org thinks it would be fantastic for the local concerned residents to take ownership of the bridge. HistoricBridges.org believes the bridge could serve non-motorized traffic for many years with very little cost and liability. Finally, a last ditch solution would be to carefully mark all the parts of this bridge's iron truss and take them apart and store them, as part of a bridge removal project. This solution would accommodate a situation where the local community did not take ownership of the bridge and Franklin County remained insistent on removing the bridge. By marking and storing the parts of the truss, the bridge would not be destroyed and could be restored and re-erected at a new location.
This bridge is rare and unique enough that it would not look out of place in a museum. A bridge of this significance should not be sent to the scrap year. HistoricBridges.org is hopeful that a solution that avoids the scrapping of this bridge can be developed that would hopefully work to the mutual satisfaction of all involved parties.
Information and Findings From Pennsylvania's Historic Bridge Inventory
Discussion of Bridge
The 2-span, 50'-long bridge was built ca. 1870 as a one-span cast- and wrought-iron Pratt pony truss bridge. According to a plaque, it was rebuilt in 1921, at which time the lower chords and floorbeams were encased in concrete and a pier added at midspan converting it to a two span bridge. The upper chord is composed of cast-iron pieces, each the length of one panel and spliced together by bolts. The cast-iron end posts are an uncommon, bowed, double I-shaped section. The cast-iron verticals are a bowed I-shaped section and are compression fitting with the upper chord. Several of the verticals have been replaced by newer I-beams, which can be identified because they are not bowed. The bridge is among the oldest metal truss bridges in the state, and although altered, it is an exceptional surviving example from the 1850s to 1870s period of innovation and experimentation in metal truss bridge technology. It illustrates the historically important transition period from wood to all iron truss bridges, before the availability of standard sizes of rolled wrought-iron shapes, such as I-beams, angles, and channels, allowed built-up wrought-iron members to replace cast iron. The cast-iron details are unique, and it is very likely that this bridge is a one-of-a-kind surviving example. The builder is undocumented by available records. The bridge has a national level of significance.
Discussion of Surrounding Area
The bridge carries a 1 lane road over a stream in a rural setting of active farms. A farm with a late 19th century brick residence and 20th century outbuildings is at the north end of the bridge. Approximately 200' south, the road is lined by about one half dozen, 19th century vernacular residences in Mowersville village. Alterations, such as enclosed porches, replacement siding, and additions, are common. The village does not have the cohesiveness or integrity of a historic district.
Bridge Considered Historic By Survey: Yes
Justification and Comments: Compromised but remarkable cast iron details; unknown fabricator
This bridge is tagged with the following special condition(s): Cast Iron
Original / Full Size Photos
|A collection of overview photos that show the bridge as a whole and general areas of the bridge. This gallery offers photos in the highest available resolution and file size in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer|
Original / Full Size Photos
|A collection of detail photos that document the parts, construction, and condition of the bridge. This gallery offers photos in the highest available resolution and file size in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer|
Mobile Optimized Photos
|A collection of overview photos that show the bridge as a whole and general areas of the bridge. This gallery features data-friendly, fast-loading photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer|
Mobile Optimized Photos
|A collection of detail photos that document the parts, construction, and condition of the bridge. This gallery features data-friendly, fast-loading photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer|
Full Motion Video
|Streaming video of the bridge. Also includes a higher quality downloadable video for greater clarity or offline viewing.|
Full Motion Video
|Video recording of a concrete sounding to test the concrete for deterioration. This simple test involves hitting the concrete with a hammer. A hollow sound indicates issues like delaminating and spalling that may be hidden under the surface. Good concrete has a solid ringing sound when hit. Streaming video of the bridge. Also includes a higher quality downloadable video for greater clarity or offline viewing.|
This historic bridge has been demolished. This map is shown for reference purposes only.
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