The historic marker says that this bridge was completed between 1834 and 1837, making it both the oldest surviving bridge, and the only stone bridge, still in use on the National Road in Illinois. You’ll find it on the National Road just west of Marshall. US 40 bypasses Marshall but rejoins the National Road’s path just west of here.
This is as elemental as it gets in the bridge-building craft. The first stone-arch bridges were built more than 3,000 years ago following this formula of stone precisely cut and fitted together without mortar. Pressure holds this bridge together – the keystone pushes the neighboring cut stones down and outward, creating rigidity and strength that lasts the centuries.
In constructing a stone-arch bridge, a falsework is built first, a timber structure that creates the arch’s shape. The stones are laid against the falsework until the arch is complete and can stand on its own. Really, the arch is the bridge. The stones laid around the arch’s ends form retaining walls. Dirt is heaped over the arch and is held back by the walls so that a road surface can be built on top.
But enough about bridge engineering; on to bridge aesthetics. Even though this is a particularly functional stone-arch bridge, it’s still plenty charming. I’ve ranted on this blog before about how modern steel-girder bridges have all the charm of a punch in the mouth. But with either kind of bridge, you don’t know what lurks below as you drive over it. You have to follow your curiosity and make a little time to stop and check. My travel companion and I did, and spent an enjoyable half hour exploring and taking in this structure that is pushing 180 years old.
By the way, I have heard of one other stone-arch bridge on the Illinois National Road. It’s just east of Marshall and west of Livingston on an abandoned segment of the 1920s brick road. It’s deep in a wooded area, and to reach it you would need to walk a long way past a very large No Trespassing sign. The old brick road isn’t even visible in there anymore, although peering past that foreboding sign you can see the road’s pathway as trees aren’t growing through it. I’ve seen a photo of the bridge and it looks to be intact, though smaller than this one.