The Casselman Bridge, a large single-arch structure erected in 1813, extends some 354', spanning the Casselman River. Stones are laid in an a random-coursed ashlar pattern. The height of the bridge is approximately 30' from the crown of the arch to the waterline below, while its width between the abutments is about 48'. The Casselman Bridge is in relatively sound condition. In 1911 the bridge was repaired, but today remains essentially unchanged from the time of its construction. Six steel columns support the structure on either side and do not overtly detract from its appearance. The old National Road has been supplanted by the new Route 40 and in actuality no longer exists. There is, however, a small portion of the old National Road on either side of the entrances to the Casselman Bridge. This area surrounding the bridge has been made into a public park with picnic tables in the area adjacent to the bridge.
The National Road was the Federal government's first experiment in public highway construction. Congress authorized the road's building in 1806 and by 1818 the road stretched from Cumberland, Maryland, to the Ohio River in what is today West Virginia. Because of the controversy regarding the propriety of the national government's participation in public road construction, the project was halted until 1828. The old National Road provided ready access to the trans-Appalachian region and greatly stimulated its settlement and growth. The Casselman Bridge was an integral part of the National Road, and at its completion, possessed the largest stone arch in the United States. Built about 1813, the bridge remains a splendid paradigm of early American engineering prowess. A traveler of the period spoke of it in laudatory terms calling it simply "superb."