is the northern extension of the Blue Ridge Mountain range
. From the Potomac River
near Knoxville, Maryland
in the south, to Dillsburg, Pennsylvania
in the north, the long range separates the Hagerstown
valleys from the Piedmont
regions of the two states. The Appalachian National Scenic Trail
follows the crest of the mountain through Maryland and part of its portion in Pennsylvania.
South Mountain begins at the Potomac River as a low, narrow ridge, barely one mile wide and only above sea level at its crest. South of the Potomac River in Virginia
, the ridge continues as Short Hill Mountain
for about before subsiding near the town of Hillsboro
. South Mountain in Maryland gradually grows higher and wider towards the north. Near the Pennsylvania border, the mountain merges with the hills of the parallel Catoctin Mountain
range to the east and becomes more like a low mountain range than a single crest. North of U.S. Route 30
in Pennsylvania, the South Mountain highlands reach their greatest width, over , and several summits top . The mountain then turns more to the east and becomes a series of small rocky hills between Mount Holly Springs
and the northeastern end of the mountain at Dillsburg.
From south to north: