From the monument:
Army of the Potomac
Fifth U.S. Artillery
Four 3 inch Rifles
Lieut. Malbone F. Watson commanding
July 2 About 4:30 p.m. arrived and took position north of Little Round Top 5:30 moved to the front at the Peach Orchard. On the advance of the Confederates driving back the infantry the Battery was retired across Plum Run near the Trostle House and fired shell and canister at the approaching Confederates until the Battery disabled by the loss of men and horses was captured by the 21st Mississippi Infantry. It was almost immediately recaptured with the assistance of the 39th New York Infantry and being unserviceable was taken to the Artillery Brigade.
Casualties: killed 1 man, wounded 1 officer and 18 men, missing 2 men
See more on the history of the 5th United States Artillery, Battery I in the Civil War