Oliver Otis Howard, Autobiography of Oliver Otis Howard, major general , United States army : volume 1

Meanwhile, Burnside's wing, followed by the remainder of Sumner's forces, hurried straight forward to Turner's Gap on the direct road from Frederick to Hagerstown. This part of the South Mountain is a mountain indeed, much wooded, very rugged, and steep. The National road leads from one side straight up through the natural depression, which is named Turner's Gap. A road to the right, called the old Hagerstown road, after leading to the north, comes back into the National road at the summit. Another highway crosses the mountain a mile or so to the south of the National road, and is called the old Sharpsburg road. Should we ascend by the one to the right of the turnpike, we would wind around a spur and find a small valley between this spur and the main ridge. This valley was occupied by the enemy. The Confederates found a crossroad near the crest. Along this crossroad D. H. Hill arranged his brigades. Both to the north and south of the National road fine locations for cannon were selected and occupied by him. Some were placed so as to sweep a high point well to the north, rather too commanding to admit of possession by an enemy. This, a sort of peak, every engineer called the key of the position. From it two distinct mountain crests coursed off southward for a mile or more with hardly a break. These crests protected the little summit valley and D. H. Hill's Confederates held them.

The evening of the 13th Pleasonton followed Stuart to the mouth of the gap. Feeling instinctively that the Confederates would occupy and defend such a defile he dismounted half of his men and sent them up the old Hagerstown road. They were soon stopped by