The monument to Battery D of the 2nd United States Artillery is south of Gettysburg on Taneytown Road. It arrived on the field on the last day of the battle and was placed in reserve. It did not suffer any casualties.
The battery is also referenced on a War Department marker at Antietam.
From the monument:
Army of the Potomac
Battery D Second U. S. Artillery
four light 12 pounders
Lieut. Edward B. Wiliston commanding
July 3. Arrived with the Corps and took position and remained on Taneytown Road.
Location of the monument
The monument to Battery D is south of Gettysburg on the east side of Taneytown Road.
See more on the history of Battery D, 2nd U. S. Artillery in the Civil War