At its west end, it continues as the Bridgeport Subdivision. The Mountain Subdivision's summit is at Altamont, Maryland, at the west end of the Seventeen Mile Grade; the grade's east end is at Piedmont, West Virginia.
In its westward section, the path turns into the Bridgeport Subdivision. The peak of the Mountain Subdivision is located at Altamont, Maryland, at the westernmost point of the Seventeen Mile Grade; the grade's eastern terminus is in Piedmont, West Virginia.