Update On The Mystery Bridge Nr. 62: The Bridge At Pontiac Lane

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A couple months ago, I posted a Mystery Bridge article about one of the bridges in Harrison County, Iowa, based on a tip provided to me by a local familiar with the bridge. This bridge is located at Pontiac Lane, just off 220nd Street, two miles east of Hwy. 30 in Logan. As mentioned in the article, the bridge was unusual because of its length over a small creek, and it was a through truss bridge, according to the online maps. There were many questions about this structure, including its aesthetic appearance, age, and the date of when it was replaced by a culvert but left in place. There was a sense of hope that someone might take a look at the structure and provide some pics for it, to help solve the case.

This is where Adrian Brisee comes in.

 

A couple weeks before Christmas, he took the opportunity to visit the bridge and provide some pics for others to see. These pics will surprise you:

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From observation, the bridge is a single lane through truss bridge of Whipple type, with pinned connections. The diagonal and vertical beams are connected with a loop. The portal bracings are a three-layer set, where the top and bottom layers are Howe Lattice (with the bottom having heel bracings) and the middle has an X-shape. This puts the date of construction back to between 1870 and 1885, when these portals were used. It also narrowed down to the number of bridge builders who used it, including Wrought Iron Bridge, King and even some of the companies in Ohio and Pennsylvania, many of whom were consolidated into American Bridge Company in 1900. The portals were subsequentially phased out in favor of those with letters, like the A-frame, X-frame, etc.  Additional markings however suggest that this was a Wrought Iron Bridge product, namely the star-engravings at each of the bottom latteral chord, as shown in the picture. This is typical of all WIBCo as 70% of their bridges have this, including the Freeport Bridge in Decorah and the Hungry Hollow Bridge near Mankato (now extant).  Judging by the length of the bridge, it is between 130 and 180 feet long; the width between 15 and 17 feet.

 

Establishing a concrete basis for solving this case, the next questions require some in-depth research and even photographing some of finest points, including inscriptions in the beams, possible connections that are either typical of WIBCo or unusual of any truss bridge built during the given period and even plaque or any additional info- enough to justify its listing on the National Register of Historic Places. This include three very important ones left to be answered:

 

  1. When was the bridge built?
  2. Was this bridge originally built at this location or was it relocated from elsewhere and if so, where?
  3. Was there a previous structure before this bridge?

 

This is in addition to the ones left to be answered. The questions are important for the condition of the bridge has deteriorated over the years, with the western side dropping three feet, thus bending the entrance noticeably. With its nomination to the National Register, funding would be made available on the state and federal levels to restore the structure and convert the area to a park. Given its unique history involving historic bridges, including some imported from out of state, Harrison County would profit greatly from having some sort of historic bridge park or district with tour guide with a list of historic bridges to visit, just like in Madison County.

 

But before we can nominate this bridge, we have some questions to clear up, which can only be done by hopping into the car, driving to the bridge for some pics and lastly, visiting the library, museum and highway department, for starters.  Having international recognition in the category of Mystery Bridge (a fifth place finish) is a start. The next ones are all yours to take.

 

So go for it. 🙂

 

If you haven’t read the results of the Ammann Awards or the Author’s Choice, please click here to take a look to see if your bridge received one of the two or both.

The Author would like to thank Adrian Brisee for visiting this bridge and taking some pics. You were of great help! 🙂

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