The East River Mountain Tunnel, connecting Virginia and West Virginia, is one of only two instances in the United States where a mountain road tunnel crosses a state line.
The East River Mountain Tunnel is a 5,412-foot (1,650 m) vehicular tunnel that carries Interstate 77 (I-77) and U.S. Route 52 (US 52) through East River Mountain between the communities of Bluefield, West Virginia, and Rocky Gap, Virginia.
Groundbreaking began on the tunnel on August 12, 1969, and after five years of labor it was opened to the public at a ribbon-cutting ceremony on December 20, 1974. At a cost of $40 million, it was (at the time) the most expensive construction project undertaken by the West Virginia Division of Highways. Because the northern end of the tunnel is in West Virginia and the southern end is in Virginia, Virginia shared the cost of the project. The state line falls almost exactly across the midpoint of the tunnel, with 51% of the tunnel residing in West Virginia and the remaining 49% on the Virginia side.
Prior to the opening of the East River Mountain Tunnel, travelers wishing to cross the state line had to navigate the narrow, twisting, guardrail-less route of US 52 up and over the mountain (now designated as VA 598/WV 598). When fog or snow was present, the journey became arduous, and the road was occasionally closed completely (particularly in the winter months) due to treacherous conditions.