The Swift River Covered Bridge in Conway, NH, was constructed in 1869. Why are bridges covered you might ask? It seems it was to protect the main wooden structural supports from moisture and rot. It was not to keep the weight of snow off the roadway as some suggest. In fact, the bridge tender was required to keep snow on the bridge so the horse drawn sleigh runners could slide freely.
Much like the strength of the curve of an eggshell, the bridge arch is unusually strong in supporting the weight of the bridge itself and the traffic thereon. Imagine for a moment, how does one build a bridge like this without modern cranes and steel beams, etc.? They were some pretty resourceful people back in those days.
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