Maryland Route 51 (MD 51) is a state highway in the U.S. state of Maryland. Known for most of its length as Oldtown Road, the state highway runs 25.53 miles (41.09 km) from an interchange with Interstate 68 (I-68) in Cumberland east to the West Virginia state line at the Potomac River, where the highway continues east as West Virginia Route 9 (WV 9) toward Paw Paw. Around Cumberland, MD 51 is a major highway that provides a bypass of the South End neighborhood of that city and access to industrial areas along the North Branch Potomac River. East of North Branch, MD 51 is a rural highway connecting small communities along the river in southeastern Allegany County, including Oldtown.