South Mountain (eastern Pennsylvania)

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South Mountain
Allentown viewed from Egypt.jpg
South Mountain as viewed from Egypt, with Allentown in the foreground
Highest point
PeakWomelsdorf Benchmark[1]
Elevation1,380 ft (420 m)
Coordinates40°19′28″N 76°11′44″W / 40.32444°N 76.19556°W / 40.32444; -76.19556
CountryUnited States
RegionNew England province
CountiesBerks, Lancaster, Lebanon Northampton and Lehigh
Parent rangeAppalachian Highlands
Borders onLebanon Valley, Lehigh Valley and Piedmont
BiomeRidge-and-Valley Appalachians
OrogenyGrenville orogeny
Age of rockProterozoic eon and about 570 to 1,600 million years ago
Type of rockCrystalline metamorphic rock and gneiss

South Mountain is a colloquial name applied to features in the mountain range extending north and northeast along the south side of the Lebanon Valley to the Lehigh Valley region of Pennsylvania. At times, it also been known as Texter Mountain, Durham Hills, Reading Hills, and the Lehigh Mountains. It is called the Reading Prong by geologists.[2] The name South Mountain is applied to the southernmost cluster of peaks in the feature, straddling Berks, Lancaster, and Lebanon counties;[3] and also to the northernmost end of the feature as the ridge into which Lehigh University is built.

South Mountain borders Emmaus, just to the south of Allentown, and comprises a ridge of low mountains passing east of Reading and then extending nearly due west. It is a continuation of the New England Province and is the southern end of the Hudson Highlands.[4]

The ridge does not follow a straight line like Blue Mountain, located to the north.

South Mountain ranges in elevation between 500 and 1,300 feet (150 and 400 m) above sea level. The ridge is made of metamorphic rocks and gneiss, which date to the Precambrian era and range from about 570 to 1,600 million years old.

South Mountain is largely undeveloped in its northern extension due to conservation efforts and its steep slope. This makes it a beautiful backdrop to the viewpoints of the Lehigh Valley, including, at night, the city lights of Allentown. The southern end of this feature extends west along U.S. Route 422 and the southeastern border of Berks County, providing views of Blue Mountain to the north, and Mount Penn (which comprises part of the prong) and the city of Reading to the east. The southernmost peaks were at one time home to many exclusive sanitariums and resorts, now all defunct except for the Caron Foundation. South Mountain serves as the transmitter site for local radio and television stations; independent TV station WFMZ-TV 69 has both its transmitter and studio facilities based on the mountain, south of Allentown.


  1. ^ "Womelsdorf Benchmark". Retrieved 6 February 2016.
  2. ^ "Reading Prong Section, New England Province". Pennsylvania Geological Survey website. Retrieved 2009-09-16.
  3. ^ "South Mountain". Geographic Names Information System. United States Geological Survey. Retrieved 2009-09-15.
  4. ^ Sevon, W.D. (2000). Physiographic Provinces of Pennsylvania, Map 13. Pennsylvania Geologic Survey. Harrisburg, PA.