South Mountain

Abstract

The battle for South Mountain took place at three wind gaps through the Maryland portion of the Blue Ridge mountain range: Turner’s, Fox’s, and Crampton’s Gaps. The vastly outnumbered Confederate infantry and artillery attempted to hold the erosion-resistant quartzite ridges capping these mountain passes against Union Gen. McClellan’s aggressive maneuver to pass through the mountain range and attack Lee’s scattered divisions in the Great Valley. The Confederates were eventually pushed out of the gaps after a day’s fighting, providing Lee with critical time to assemble his army around Sharpsburg. The geology of the battlefield aided this resistance; the durability of the Weverton and Harpers Formations, composed of metamorphic quartzite and phyllite, provided high, easily defendable terrain, including large boulders and outcrops that provided natural breastworks for defense and obstacles for the attacking Union army.