HDQRS. THIRD BRIG., PENNSYLVANIA RES. VOL. CORPS,
Camp near Sharspburg, September 22, 1862.
LIEUTENANT: I have the honor to submit the following report of the part taken by this brigade in the battle of September 14:
At daylight on the morning of the 14th this brigade broke camp near Frederick, and took up the line of march in the direction of Middletown. Having passed Middletown, the command halted on the banks of the creek and rested for about one hour, when the march was resumed, in the same direction as pursued in the fore part of the day, for the distance of about a mile. We here filed to the right along a road running at right angles with the turnpike. Pursuing this road the distance of half a mile, we entered the open fields to the right of the road, when we were immediately ordered to support Cooper's battery, which had taken position on a hill to the left and looking toward South Mountain, upon which the enemy had planted and opened a battery on us as we filed through the open fields. A few shots fired by Cooper elicited no response from the enemy, and we were ordered to form a line of battle, which was done in the following order: The Ninth on the right, the Eleventh in the center, the Twelfth on the extreme left, and the Tenth as a reserve 50 or 75 paces in the rear. Our brigade now began to move obliquely to the right and front under a severe fire of artillery posted on the mountain, but which did very little, if any, damage.
Moving on, we soon met the enemy, posted at the base of the mountain and sheltered by a stone wall. The firing immediately commenced on both sides. Here Colonel Gallagher, who had command of the brigade, and who had gallantly led it into action, was severely wounded in the arm by a musket ball, and forced to leave the field. Our line moved steadily on, not once giving way or faltering. The enemy were driven from their shelter, and steadily pursued up the mountain till the summit was nearly gained by our men, when, all our ammunition having been expended, Duryea's brigade having come up and taken its position in front of us, portions of the Ninth, Eleventh, and Twelfth (through a misconception of orders) fell back to supply themselves with ammunition. The Tenth Regiment, which had been ordered forward to fill up the gap between our right and Seymour's left, and which had fought its way gallantly up to the other regiments of the brigade, was ordered to hold its position. When the Ninth, Eleventh, and Twelfth Regiments fell back it was dark, and 11 o'clock before they were supplied with ammunition. The firing having ceased before these regiments left, and our forces being in quiet possession of the crest of the mountain, it was not thought advisable to order them up the mountain again that night; another consideration being that the men were much fatigued by a long march and their exertions upon the field.
My report of the battle of South Mountain closes with the remark that it was a severe one, and that every officer and man of this command did his duty nobly.
Lieutenant-Colonel, Commanding Brigade.
Source: OFFICIAL RECORDS: Series 1, Vol 19, Part 1 (Antietam - Serial 27) , Pages 274 - 275