The monument to the First Battery, Ohio Light Artillery at Antietam is south of the battlefield on Burnside Bridge Road. (Burnside Bridge tour map) It was dedicated in 1903.
The battery was commanded at Antietam by 27 year old Captain James R. McMullin. It was armed with six 14-pounder James Rifles, which would be replaced with 10-pounder Parrott Rifles shortly after the battle.
The battery earned the nickname of the “Jackass Battery” early in the war when it was equipped with mountain howitzers drawn by unbroken mules.
From the monument:
OHIO
Monument to the
1st Battery Light Artillery
Commanded by Capt. James R. McMullin
Hugh Ewings (1st) Brig.
Kanawha Division
Ninth Army Corps
Army of the Potomac
This battery occupied position about 250 yards due west of this.
Location of the monument
See more on the history of the 1st Battery Ohio Light Artillery in the Civil War