Just northwest of Dillsburg, PA, west of Camp Ground Road in Carroll Township, York County, the great Blue Ridge Mountain Complex begins. Theoretically the Green Mountains of Vermont and even the Chic-Choc Mountains of Quebec are the same topographic feature, but here, just south of the wide Susquehanna River, mountainous terrain rises apruptly from lowlands after a long hiatus, and it continues all the way to Georgia.
This first, northernmost extention of Blue Ridge is South Mountain and its associated ridges, a large, very irregular mass covering big chunks of south-central Pennsylvania and central Maryland. Although quite low and
hardly worthy of the term "mountain", for the Mid-Atlantic area South Mountain is quite impressive, and located very close to cities such as Washington, DC and Harrisburg, PA. As a mountainous island in a sea of productive farming country, the views of the patchwork quilt of fields are nice, on those rare occasions when the trees clear out.
The Pennsylvania section of this mass, which includes extentions such as Piney Mountain (1890') to the southeast and the Carlisle Prong to the north towards Dillsburg, is largely protected by Michaux State Forest and almost entirely traversed by the Appalachian Trail. The highest point is boring Big Flat Pine Ridge (2100'), which the A.T. grazes, but the high point in the section south of U.S. 30, Snowy Mountain (2080'), has a fire tower providing fine views.
Other areas of South Mountain of special interest are the White Rocks-(1050') in the Carlisle Prong, craggy Pole Steeple (1300') on Piney Mountain, and the Chimney Rocks (1946') just south of Snowy Mountain. All are on or near the A.T., make nice, short half-day hikes, have cliffs big enough to attract rock-climbers, and provide a Pennsylvania rarity, nice views.
In Maryland, South Mountain is the western edge of the mountainous area, while a prominent and increasingly distinct ridge parallelling South Mountain to the east is Catoctin Mountain (1917'). The Appalachian Trail runs along the crest of South Mountain as it gets narrower and narrower as it approaches the Potomac, missing Mt. Quirauk (2140'), just south of the Mason-Dixon line separating Pennsylvania and Maryland, due to the presence of the Fort Ritchie Military Reservation.
Catoctin Mountain, which starts out as a wide plateau connected to South Mountain on the west, becomes a low and narrow ridge west of Frederick, MD before petering out into nothingness into Virginia. In the pleasant forests of Catoctin Mountain west of Thurmont, MD is one of the few U.S. governemnt-owned areas in the mountains where visitors are not encouraged--Camp David, the rural retreat for U.S. Presidents.
As South Mountain and the Appalachian Trail approach the Potomac River, a parallel ridge appears to the west--the genesis of the actual Blue Ridge. At the Potomac near Harpers Ferry, VA, where the river has carved a double water gap that has been impressing tourists since George Washington, the A.T. drops down off of South Mountain, follows the towpath of the old Chesapeake and Ohio Canal west to the historic town of Harpers Ferry, then climbs steeply up to the Blue Ridge, which it then follows for over 200 miles (see the Far North Blue Ridge). Across the Potomac South Mountain becomes Short Hill Mountain, which soon disapppears.