Casselman Bridge: The Longest Arch in America
Near Wisp, Maryland
Just off the highway near Grantsville, a stone arch bridge crosses the Casselman River looking exactly as it did when wagons first rolled across it more than two hundred years ago. When it opened in eighteen fifteen, it was the longest single-span stone arch bridge in the United States, and it may be the finest surviving example of early American road engineering anywhere in the country.
The bridge exists because of the National Road, the first federally funded highway in American history. In eighteen oh six, Congress commissioned David Shriver Jr., a Cumberland civil engineer, to locate and build the road westward from Cumberland through the Alleghenies. Shriver faced an engineering problem at the Casselman River, a crossing the old road called Little Crossings. He needed a bridge strong enough for heavy loaded wagons and ambitious enough to last. Construction began in eighteen thirteen.
The result is eighty feet of stone arch, rising thirty feet above the riverbed, carrying a roadway forty-eight feet wide. The stonework is twenty-six feet wide and three feet thick at the crown. Shriver reportedly designed the span wide enough to someday accommodate Chesapeake and Ohio Canal boats if they ever crossed the Alleghenies. They never did, but the ambition is remarkable.
The bridge carried National Road traffic for more than a century, from the era of Conestoga wagons through the early automobile age. It was bypassed in nineteen thirty-three when U.S. Route Forty was rerouted, and it has never carried motor vehicles since. That early retirement may be the reason it survives in such extraordinary condition.
The bridge was declared a National Historic Landmark in nineteen sixty-four, one of very few bridges in the country to hold that designation. It stands today in a small state park, open to pedestrians, unchanged since the first western settlers walked across it.
