Pennsylvania Light Artillery, Independent Battery D

"At three P. M., on the 13th [September, 1862] we went into position, near the top of South Mountain. We were very successful in this engagement, had good ammunition, twice silenced and drove off a rebel battery, and harassed the rebel infantry as they advanced on our troops on the right of our position, firing from our six guns about two hundred and fifty rounds. The next day, we moved after the enemy, toward Antietam. On the morning of the 17th, we were shelled out of camp at daylight, and immediately went into position, and opened fire in reply. At nine A. M., we were ordered to the rear of Stone Bridge, No. 3, nearly opposite Sharpsburg, and just before General Hartranft took the bridge, our centre section moved near to the bridge, and followed closely the General's infantry across. This section was soon after joined by the rest of the battery, and the whole went into position at a point about nine hundred yards from the rebel guns opposed to us, which we engaged whenever they opened, at short intervals, for upwards of two hours, and only retired when we got out of projectiles, and were ordered back, the general commanding us, not deeming it advisable to allow our caissons to cross the bridge to bring up a supply of ammunition. This was the most desperate engagement, I think, and at shortest range, which our battery was in. Our loss was two men dangerously wounded; several of our horses dropped down in their harness from exhaustion, and had to be left on the field."
(from Lt Samuel H. Rhoads, 1864, later Captain in place of Capt Durell, quoted in Bates)

Detail Map #7: Burnside Attacks the Lower Bridge (10 am-1 pm)
Detail Map #12: Burnside's Ninth Corps Climbs Toward Sharpsburg (3-4 pm)
Detail Map #13: AP Hill's Division Hits Burnside's Flank (4-5 pm)

Tablet #56: Ninth Army Corps - 15 Sep, 7 AM to 16 Sep, 3 PM
Tablet #58: Sturgis' Division, Ninth Army Corps - 16 Sep, 9 PM to 17 Sep, 5 PM
Tablet #122: Army of the Potomac - 17 Sep, 10 AM to 17 Sep, 6 PM
Tablet #70, cont: Ninth Army Corps - 17 Sep, 3 PM to 17 Sep, 5 PM
Tablet #70: Ninth Army Corps - 17 Sep, 7 AM to 17 Sep, 3 PM
Tablet #57: Ninth Army Corps - 17 Sep, 7 AM to 17 Sep, 5 PM

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