The marker for Magilton’s Brigade of Meade’s Division, September 17, is on the east side of the Hagerstown Pike just south of the North Woods. (Hagerstown Pike tour map)

Magilton's Brigade, Meade's Division, marker 12 of the War Department Union markers at AntietamFrom the marker:

U.S.A.
First Army Corps

Magilton’s Brigade, Meade’s Division

Col. A. L. Magilton, 4th Pennsylvania Reserves, Commanding.

(September 17, 1862.)

Magilton’s Brigade advanced from the North Woods about 6:30 A. M. and passing a few rods east of D. R. Miller’s house, formed line on the left of Anderson’s Brigade. A part of the Brigade supported by the 124th Pennsylvania, of the Twelfth Corps, engaged the enemy in the north edge of the Cornfield. Soon after, the Brigade was ordered to the left to the assistance of Seymour and Ricketts and, in front of the East Woods, while in motion by the left flank about 75 feet north of the Cornfield, the Brigade was fiercely assailed by the Confederates. The assault was checked by the timely arrival of Williams’ Division, Twelfth Corps, after which the Brigade was withdrawn to the fields northeast of Joseph Poffenberger’s.

No. 12.

Magilton's Brigade, Meade's Division, marker 12 of the War Department Union markers at Antietam