Interstate 68 (I-68) is a 112.9-mile (181.7 km) Interstate Highway in the U.S. states of West Virginia and Maryland, connecting I-79 in Morgantown, West Virginia, to I-70 in Hancock, Maryland. I-68 is also Corridor E of the Appalachian Development Highway System. From 1965 until the freeway's construction was completed in 1991, it was designated as U.S. Route 48 (US 48). In Maryland, the highway is known as the National Freeway, an homage to the historic National Road, which I-68 parallels between Keysers Ridge and Hancock. The freeway mainly spans rural areas and crosses numerous mountain ridges along its route. A road cut at Sideling Hill exposed geological features of the mountain and has become a tourist attraction.