The monument at Antietam to the 3rd Delaware Volunteer Infantry Regiment is the West Woods in Philadelphia Brigade Park. (Philadelphia Brigade Park tour map; 39°28’44.6″N 77°44’58.3″W; map location) It was dedicated on May 30, 1964.

The 3d Delaware was commanded at the Battle of Antietam by Major Arthur Maginnis. When he was wounded Captain William J. McKaig of Company F took over. The regiment had suffered heavily at the Second Battle of Bull Run two weeks prior to Antietam and brought only 5 officers and 120 men to the field. These were organized into four companies, one of which was detached as skirmishers. The remaining companies took position on the left of the brigade line in a woods about 250 yards from the enemy, remaining there four hours under heavy fire.

Monument to the 3rd Delaware Volunteer Infantry Regiment on the Antietam battlefieldFrom the monument:

Delaware

3rd Delaware Volunteers

Major Arthur Maginnis
3rd Brigade, 2nd Division, XII Corps

This regiment, worn down from active service in the second Manassas Campaign, went into action Sept. 17, 1862 with only five officers and 120 men. It started out on the right of the Union line in front of the West Woods. After heavy action along the Hagerstown Pike, it helped repulse Confederate counter attack following rout of Sedgewick’s Division. Final position of the regiment, 65 yards North of this point.

Losses
Officers Men
Killed 1 5
Wounded 2 9

Total 17 of 125 engaged

Erected by the Delaware Civil War Centennial Commission May 30, 1964

See more about the 3rd Delaware Volunteer Infantry Regiment in the Civil War