A monument to the 3rd Maine Volunteers is south of Gettysburg in in the Peach Orchard (39.800411° N, 77.250067° W; Tour map: Peach Orchard). Two position markers are on Berdan Avenue west of West Confederate Avenue (39.808004° N, 77.257255° W; Tour map: West Confederate Avenue – Pt. 4) and on Hancock Avenue across from the Copse of Trees. (39.81249° N, 77.23529° W; Tour map: Hancock Avenue at The Angle; Google maps to all 3 monuments)
The 3rd Maine was commanded at the Battle of Gettysburg by Colonel Moses B. Lakeman. Lakeman took over the brigade on July 3rd, and Captain William C. Morgan took command of the regiment.
From the front of the monument:
3rd Maine Inft’y
2nd Brigade 1st Division 3rd Corps
Strength of regiment morning of July 2nd
14 officers and 196 men

Closeup of the left side of the monument.
From the left (west) side:
Detached from the Brigade. Fought here in the afternoon of July 2nd, 1863.
Having been engaged in the forenoon at point in advance as indicated by a marker.
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July 3rd in position on left centre of line, until afternoon, when with other regiments of the Brigade, it moved to support of the centre at time of the enemy’s assault.
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1 officer and 17 men killed, 2 officers and 57 men wounded, 45 men missing.

From the Hancock Avenue marker:
3rd Maine Regiment
Colonel M. B. Lakeman
In support July 3rd 1863;
Engaged July 2nd in Peach Orchard

Position marker for the 3rd Maine on Berdan Avenue
(off West Confederate Avenue)
3rd Maine Infantry
engaged here forenoon of July 2nd 1863

Looking southeast from the Peach Orchard. Big Round Top is in the distance to the right of the monument.
See more on the 3rd Maine Volunteer Infantry Regiment in the Civil War