That’s a little bridge over a little creek. It was built in 1913 to carry an interurban trolley over Jowler Creek near the small town of Camden Point, Missouri. The route of the trolley is now Interurban Road, and after the trolley company failed in 1933, the bridge was converted to carry car traffic. Interurban trolleys are less well-known today than their urban counterparts, but they were electric mass transportation connecting towns in areas without enough traffic to justify heavy rail. Today, routes like that are served by busses (where they exist at all), but we could do a lot worse for future transportation planning than looking at restoring interurbans.
What caught my eye as I was paging through the HABS/HAER index was the name “Luten arch.” This bridge is an example of a Luten arch and I’d never heard of it. Civil engineering and the history of construction are huge topics, so I can always find something new to learn. It turns out that this is not a specific form of arch, it’s a concrete arch designed by Daniel Luten, who was an early entrant into the concrete-brdge field in the US. He patented his designs and worked with various contractors to build them. Again, fairly ordinary stuff, until you get to the claim by Luten, in 1919, that he had designed 17,000 bridges. (The HAER historian for this bridge says 12,000, but I’ll state here my belief that is still an amazing number.) The reason that I don’t immediately dismiss that as impossible is that he used standardized designs, to the point where he had a formula for the cost based on simple variables like span and width. He wasn’t looking to design record-breaking or amazing spans, he was looking to design a lot of bridges.
Let’s put this in perceptive. The 2021 “Infrastructure Report Card” from the American Society of Civil Engineers says that there are over 617,000 bridges in the US. (The 2017 Report Card said there were 614,387 bridges. I wonder if someone asked if the engineers at the ASCE if they carry six significant figures the they perform calculations.) Using the low estimate of 12,000 bridges for Luten, his work was the equivalent of two percent of the bridges we have today, but there were fewer bridges in 1920, as the population of the country was less than a third of what it is now. This is an amazing amount of work by any standard.
How was this possible? In the same way that (to use an example more closely related to my work and which I researched for the Seventh International Congress On Construction History) Charles Buddensiek was able to build 2,000 out of the 80,000 tenement buildings that existed in New York in 1900: repetition. If you focus on a single problem and simply repeat variations on your successful answer, you save a lot of time compared to looking for a new solution each time.