The marker for Meagher’s Brigade of Richardson’s Division is on the north side of the Sunken Road. (Sunken Road East tour map)Meagher's Brigade, Richardson's Division, marker 46 of the War Department Union markers at Antietam

From the marker:

U.S.A.

Meagher’s Brigade, Richardson’s Division

Brig. Gen. Thomas F. Meagher, Commanding.

Organization.
29th Massachusetts Infantry
63d New York Infantry
69th New York Infantry
88th New York Infantry

September 17, 1862. 

Meagher’s Brigade led the advance of Richardson’s Division and, in the field just north of this, became engaged with the Confederate Brigade of Geo. T. Anderson, which was forced to retire to the Bloody Lane.

At this point, Meagher’s advance was checked and a severe contest ensued, but 30 yards separating the opposing lines.

Its ammunition having been exhausted, the Brigade was relieved by Caldwell’s but, later in the day, advanced to a position on the high ground, south of this point, in suport of Caldwell and Brooke.

No. 46.

See the Order of Battle for Richardson’s Division of the Second Corps at Antietam.