At the battle of South Mountain, September 14th, the Second Corps was in reserve, but when the pass was carried, was immediately thrown forward, through Boonsboro', to Keedysville, on the Antietam. In the meantime, General Burns had been promoted to the command of a division in the Ninth Corps, and General O. O. Howard had been assigned to the command of the brigade. The enemy was now in front, and the corps was posted in support of a line of batteries on the left bank of the creek, on which he opened early on the following morning. It was promptly responded to, when, as if by mutual consent, the firing suddenly ceased, and for some time both sides remaned silent; but it was fitfully renewed during the day.

0n the morning of the 17th, wading the Antietam Creek, which was here waist leep, the division made a sharp detour to the right, and then turned abrupty to the left, where, at ten A. M., in marching through the never-to-beforgotten corn-field, it found itself face to face with the enemy. Before reaching the field, the division had been thrown into parallel lines by brigade front, at a distance of seventy paces apart. In this order it advanced under a heavy artillery fire from guns posted on the Hagerstown road, and drove the enemy's infantry, concealed in the tall corn, steadily before it, until he reached a position beyond the hill, on which he had judiciously posted his artillery, and from which he had poured forth his fire with terrible effect. Here. his infantry, reinforced, took shelter in a sunken roadbed, which formed a natural rifle-pit, and delivered a galling fire upon Sedgwick's column, which was, at the same time, subjected to a hot fire from the foe still concealed in the corn-field. The fire of musketry and artillery from either side, now at short range, was appalling.

Here General Sedgwick was wounded and borne from the field, the command devolving on General Howard. The division had entered the belt of woods west of the turnpike, and near the Dunker Church, and was steadily pushing the enemy back upon his earth-works, when it was discovered that the troops holding the left of the line had been driven in. It had now a heavy infantry and artillery fire upon its front, and also a galling enfilading fire upon its flank.

General Sumner, who was most conspicuous, riding upon every part of the field, ordered General Howard to change front and lead his command against the troops upon his left. In executing the movement, a part of the troops fell into some confusion. But the Seventy-first stood firm, and, with the Nineteenth Massachusetts, charged full upon the foe, now advancing in triumph, and with unearthly yells. Wistar, who headed the charge, fell severely wounded, and for three hours the tide of battle ebbed and flowed over him before he could be removed. Adjutant Smith, who had been acting as a field officer upon the left of the line, with Deveraux, who led the Nineteenth, pushed on unmindful of disaster, but had scarcely reached the enemy when he also fell. The command now devolved on Captain Lewis, who succeeded, after repelling several attacks, in bringing the regiment into position at the Dunker Church, where, at the close of the battle, it rested. The loss was over one'-third of the entire number engaged, and on the morning of the 18th only four officers were present for duty. Lieutenants John Convery and William Wilson were among the killed.

Soon after this battle Colonel Wistar was promoted to Brigadier General. Lieutenant Colonel Markoe, who had been promoted from Captain of company A to Major, and to Lieutenant Colonel, had resigned on account of wounds. and had been re-commissioned, now returned and assumed command of the regiment. Before entering upon the Fredericksburg campaign, under Burrside, General Couch was assigned to the command of the Second Corps, General Howard of the Second Division, and Colonel Owen of the Second Brigade, General Sumner commanding the right grand division, composed of the Second and Ninth Corps.

Source:

Bates, Samuel P. History of the Pennsylvania Volunteers, 1861-65, Harrisburg, 1868-1871.