Marty shared this photo and also some information about the CR510 Pennsylvania Truss Bridge in Marquette County from historicbridges.org:
This is one of the largest, most beautiful, and most significant truss spans in Michigan. Not only does this truss bridge display the Pennsylvania truss configuration, it appears that it may have actually come from the state of Pennsylvania. In 1919, the Michigan State Highway Department purchased the bridge which originally crossed the Allegheny River. Relocating and reusing truss bridges was not unusual in this period of history. An example notice indicating bridges for sale from 1921 is shown to the right. At this time, CR-510 was a state trunk line route and purchasing and relocating this bridge would have been an inexpensive alternative to building a new bridge from scratch. It was erected on the CR-510 location in 1921. The Michigan State Highway Department’s Biennial Report stated that the bridge was one of two toll bridges crossing the Allegheny River within 500 feet of each other and was being removed due to the redundancy. Unfortunately, the report did not state exactly where on the river this bridge came from. Since most of the Allegheny River is in Pennsylvania, it is assumed the bridge came from Pennsylvania, although the Allegheny River does dip into New York State for a short time. Depending on where on the Allegheny River it was originally located, it may have been part of a multi-span bridge.
Pennsylvania truss bridges are an uncommon truss type, and the nature of their design means that they are reserved for longer truss spans. However, even among pin-connected highway Pennsylvania truss spans, this bridge’s span still stands out as fairly long. It is the longest pin-connected highway truss span in Michigan. The truss type is extremely rare in Michigan, and so the bridge has additional significance in the context of Michigan. The bridge also retains excellent historic integrity with minimal alterations despite its long service and being located in two different states over its service life. The bridge has decorative details on its portal bracing, another feature that is rare among Michigan truss bridges.
Read on for more.
More bridges on Michigan in Pictures.