Mystery Bridge Nr. 128: The Disappearing Thacher Truss Bridge in Castlewood, SD

BHC Mystery Bridge

This Mystery Bridge entry takes us to the town of Castlewood in Hamlin County, The town is located east of the Big Sioux River, which snakes its way through the field in its infancy before it widens near Watertown. While Castlewood may be a typical rural American town, it does hold a treasure that is historically significant and one where we’re looking for.

The Castlewood Truss Bridge was a Thacher through truss bridge that had spanned the Big Sioux River southeast of town. It carries 184th street. The structure is 100 feet long with the main span having been 80 feet. The bridge was built by the King Bridge Company in 1894 under the direction of agent Milo Adams, and was the second of two bridges that was discovered and researched by the National Park Service in 1989. The second was at Yellow Bank Church Bridge in Laq Qui Parle County in neighboring Minnesota, built one year earlier. . Together with the Ellworth Ranch Bridge in Emmet County, Iowa, the Castlewood Bridge represented an example of the hybrid form of the Thacher Truss Bridge, which was patented by Edwin Thacher in 1881.

The bridge was listed on the National Register of Historic Places on December 9th, 1993, yet the bridge was replaced on a new alignment by a low-water crossing in the summer of 1990. According to recent satellite view, the Thacher Truss structure is no-more. All that is left are the wing-walls and the lally columns on the west bank of the river.

This leads us to the main question: What happened to the bridge?

Research in newspaper articles and correspondences have thus far come up with nothing concrete. The exception was the plan to replace the bridge in 1989 after reports revealed that the structure was rusting and no longer able to carry traffic, which ran parallel to the research into the bridge’s historic significance. Bridgehunter.com had pinpointed the replacement date as sometime after June 1990, even though the article mentioned August 1990 as its planned replacement date.

This leads us to why the Castlewood Bridge was listed before the end of 1993. According to the National Register of Historic Places, any historic structure can be listed on the register if they comply to the requirements of historic significance. Once it’s listed, then grants and funding are made available for restoring and protecting the place, and it is next to impossible to demolish the historic place unless plausible arguments are made justifying it, which includes understanding the consequences of destroying it, which is its delisting. If the Castlewood Bridge was demolished for any reason, the bridge would be delisted from the National Register, and all records pertaining to its nomination, history and the like would be archived and made unavailable for researchers. If the bridge was replaced before its nomination in 1993, why list the structure to begin with? And if it was destroyed after its listing in 1993, why is it still listed?

This leads us to the question of what happened to the Castlewood Bridge. One has to assume that the bridge was dismantled and put into storage to be reused elsewhere. This was what happened to the Yellow Bank Church Bridge, and the truss bridge now has a new home at the historic village park south of Hastings in Minnesota. Its role is mimicking the Famous Hastings Spiral Bridge, the first bridge in the world with a loop approach. With regards to the Castlewood Bridge, the question is: Where’s the bridge? And will it be reused somewhere, if it has not been re-erected already? If the bridge no longer exist, then the question is 1. Why justify its existence on the National Register, and 2. Were any bridge parts been preserved as a historical marker?

The research about the bridge’s fate has not born any fruit to date. Therefore, the question goes straight to the locals of Hamlin County, South Dakota and the residents of Castlewood with this in mind:

“Where’s the Bridge?”

BHC 10 years

5 thoughts on “Mystery Bridge Nr. 128: The Disappearing Thacher Truss Bridge in Castlewood, SD

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