Mystery Bridge 35: Deck Pennsylvania Petit truss bridge in Wisconsin

Pennsylvania petit truss bridges- one of the most used truss bridge types for long crossings of 130 feet and longer. As I wrote a few months earlier, Pennsylvania trusses were used as often as Pratt, Parker and Warren trusses for bridge construction between 1875, the year it was patented, and 1940, when steel was diverted away from bridge building for the war effort, although only a handful of examples exist in each state of the US, and have been documented by the state historic preservation offices. Iowa was one of those examples (click here for more details).  Yet Pennsylvania truss bridges were used exclusively for through truss spans, like the Old Rusty Bridge north of Spencer,Iowa, as shown in the picture above, right?


Fellow pontist Luke Harden presented a unique find that featured a Pennsylvania truss bridge that was not a through truss, but a deck truss. Located in Lake Delton in Sauk County, Wisconsin, the bridge clearly shows the characteristics of a Pennsylvania truss bridge but built in a reciprocal fashion with the truss supporting the deck.  A picture of the bridge can be seen via link here. Spanning Dell Creek shortly before it empties into Mirror Lake, the bridge was reportedly built in 1908 and was between 170 and 200 feet long. It was built next to Timme Mill and Dam. The dam was constructed in 1857 and the mill existed from 1849 until it was burned down in 1957. It was the same fire that caused extensive damage to the bridge itself, and despite repairs made on the structure, its days were numbered. The bridge was demolished in the 1980s although data presents conflicting facts- one claimed it was 1981, the other 1986. In either case, the bridge was dropped into Dell Creek, surviving the impact unscratched! It was later cut up and sold for scrap metal.

The bridge was an impressive one that never deserved to be sentenced to the scrap heap, yet Wisconsin’s record in preserving places of historic places- in particular historic bridges- has always been questionable, for over 80% of the bridges built up to 1960 have disappeared since 1980. Had the preservation policies worked like in neighboring Illinois, Indiana and Iowa, chances would have been most likely that the bridge would still be standing today. Yet its demise leads to some questions that need to be clarified. Apart from determining when exactly the bridge was dropped into Dell Creek, it is important to know the exact length and width of this truss bridge and who was behind the construction of the bridge- let alone why it was built that way. My hunches are that either Horace Horton, who constructed many unusual truss bridges during his days as bridge builder may have been behind it. Yet we also have the Clinton Bridge and Iron Works, which built many Pennsylvania truss bridges in Iowa and may have built this one, because of its proximity to Wisconsin (on the Mississippi River). But the Wisconsin and Minnesota bridge builders were also influential in building bridges during that time, so they must be included.

In either case, information on how the bridge was built, etc. should be posted here or under facebook or LinkedIn. As it is posted on under the name Upside-Down Bridge in Sauk County, you can add your comments there as well. In either case, enquiring minds wants to know with regards to the history of this bridge. And the Chronicles is there to ensure that the mystery of bridges like this one is solved. So happy hunting and here with the info! 🙂

One thought on “Mystery Bridge 35: Deck Pennsylvania Petit truss bridge in Wisconsin

  1. Hey man, love the info! Do you know if the Pennsylvania truss has any disadvantages? I was also wondering where the tension and compression lie.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.