The monument to the United States Battalion of Engineers is south of Gettysburg on Pleasonton Avenue. (Google map; Tour map: Pleasonton Avenue). Like many of the other units whose monuments are on Pleasonton Avenue, the Battalion was not at the battle but took part in a support role in the campaign.
From the monument:
Army of the Potomac
United States Battalion of Engineers
Capt. George H. Mendell Commanding
With the Army of the Potomac in the Gettysburg Campaign from the Rappahannock to the Potomac and engaged in arduous duties from June 13th to July 18th bridging rivers and transporting pontoons.
No casualties reported