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.The name South Mountain is applied to the southernmost cluster of peaks in the feature, straddling Berks, Lancaster, and Lebanon counties; and also to the northernmost end of the feature as the ridge into which Lehigh University is built.