The monument to the 5th Maine Volunteers is south of Gettysburg on the west side of Sedgwick Avenue just north of Wheatfield Road. (39.795311° N, 77.235006° W; Google map; Tour map: Sedgwick Avenue) It was erected in 1889 by the State of Maine.
The 5th Maine was commanded at the Battle of Gettysburg by Colonel Clark S. Edwards. It brought 340 men to the field and suffered no casualties.
From the monument:
5th Maine Infantry
2nd Brig. 1st Div. 6th Corps
Occupied this position from evening of July 2nd until close of battle.
Mustered into the U.S. Service Portland, Me. June 24, 1861. Served with the Army of the Potomac in the field from Bull Run to Petersburg. Mustered out, Portland, June 27,1864.
See more on the 5th Maine Volunteer Infantry Regiment in the Civil War