The pair of markers for Irwin’s Brigade of Smith’s Division are on the north side of the Sunken Road north of the Mumma Farm Lane. (Sunken Road west tour map)

From the first marker:

U.S.A.
Sixth Army Corps

Irwin’s Brigade, Smith’s Division

Col. William H. Irwin, 49th Pennsylvania Infantry, Commanding.

Organization.

7th Maine Infantry
20th 33d, 49th and 77th New York Infantry

September 17, 1862.

Irwin’s Brigade came on the field about noon of the 17th, and formed across the Smoketown Road in rear of a line of Artillery.

After an unsuccessful attempt to penetrate the Confederate line south of the Dunkard Church, the Brigade rallied behind the ridge east of the Hagerstown Pike and between it and Mumma’s Lane, the left of the Brigade resting a few yards west of the lane, where it was exposed to a severe fire of Artillery and Sharpshooters.

No. 74.

From the adjacent marker:

No. 74 Continued.

About 5 P.M., the 7th Maine, on the left of the Brigade, crossed Mumma’s Lane, moved obliquely across the front of Brook’s Brigade, charged over the Bloody Lane at this point, dispersed the Confederates in its front and in the orchard on its left and reached the low ground North of Piper’s Barn, when the enemy from behind the stone fence on the Hagerstown Pike and the hill adjoining poured a severe fire on its right flank and front.

The regiment then obliqued to the left, passed through an opening in the fence into the orchard and to within 70 yards of Piper’s House, here it was met by a withering fire from a column of the enemy moving down the hill east of the house and driven back through the orchard with great loss.

It reformed a short distance east of this point and returned to the position from which it had advanced.

At noon of the 18th, the Brigade was relieved by Cochrane’s Brigade of Couch’s Division.