The 138th Pennsylvania Volunteer Infantry Regiment lost 10 officers and 135 enlisted men killed and mortally wounded and 5 officers and 86 enlisted men by disease, a total of 236. It is honored by two monuments at Gettysburg.

1862
September 1 Organized at Pittsburg
September 1-3 Moved to Washington, D.C. and attached to 2nd Brigade, 1st Division, 4th Army Corps, Army of the Potomac
September 4-7 Bury dead at Bull Run, Va.
September 7-24 Maryland Campaign. Attached to 2nd Brigade, 3rd Division, 6th Army Corps, Army of the Potomac
September 16-17
Battle of Antietam

The regiment was in Pleasant Valley during the battle and did not reach the battlefield until the 18th.

September 23-October 20 At Downsville
October 20-November 18 Movement to Stafford Court House. Attached to 3rd Brigade, 3rd Division, 6th Army Corps
December 5 To Belle Plains
December 12-15 Battle of Fredericksburg, Va.
1863
January 20-24 Burnside’s 2nd Campaign, “Mud March”
February-April At Falmouth
April 27-May 6 Chancellorsville Campaign
April 29-May 2 Operations at Franklin’s Crossing
May 3 Maryes Heights, Fredericksburg
May 3-4
Salem Heights
May 4 Banks’ Ford
June 13-July 24 Gettysburg Campaign
July 2-4
Battle of Gettysburg

The regiment was commanded by Colonel Frederick H. Collier until he was wounded on July 3rd. Lieutenant Colonel William H. Moody then took command.

From the monument on the John Weickert farm at Gettysburg:

Left Manchester, Md. at 9 p.m. July 1st and arrived at Rock Creek on the Baltimore Pike at 2 p.m. of the 2nd. Towards evening the Brigade moved rapidly to the front to support the Union left, this Regiment deploying on the right of Little Round Top, and advanced with the 1st Brigade Penna. Reserves, driving the enemy into the Wheatfield.”

Retired to and held this position until the evening of the 3rd when the Regiment moved with the Penna. Reserve and advanced about 900 yards to the position indicated by a greek cross tablet, and assisted in forcing the enemy back. Subsequently returned to this position.

Present at Gettysburg 511. Killed and mortally wounded 4, wounded 16.

July 5-24 Pursuit of Lee
August-Otcober Duty on line of the Rappahannock and Rapidan
October 9-22 Bristoe Campaign
November 7-8 Advance to line of the Rappahannock
November 7 Rappahannock Station
November 26-December 2 Mine Run Campaign
December At Harper’s Ferry
1864
January Attached to Wheaton’s Brigade, Dept. of West Virginia
March Attached to 1st Brigade, 2nd Division, 6th Army Corps, Army of the Potomac
May 4-June 12 Rapidan Campaign
May 5-7
Battle of the Wilderness
May 8-21
Battle of Spotsylvania Court House
May 12 Assault on the Salient
May 23-26 North Anna River
May 26-28 On line of the Pamunkey
May 28-31 Totopotomoy
June 1-12
Cold Harbor
June 17-18 First Assault on  Petersburg
June 22-23 Jerusalem Plank Road, Weldon Railroad
July 9 Siege of Petersburg
July 9-11 Moved to Washington, D.C.
July 11-12 Repulse of Early’s attack on Washington
July 14-24 Pursuit to Snicker’s Gap
August to December Sheridan’s Shenandoah Valley Campaign; attached to Army of the Shenandoah
August 13 Near Strasburg
August 21-22 Near Charlestown
September 13 Demonstration on Gilbert’s Ford, Opequan
September 19
Third Battle of Winchester (Opequan)
September 21 Strasburg
September 22
Fisher’s Hill
October 19
Battle of Cedar Creek
October-December Duty in the Shenandoah Valley
December 9-12 Moved to Petersburg, Va.
December Siege of Petersburg
1865
February 5-7 Dabney’s Mills, Hatcher’s Run
March 25 Fort Fisher, Petersburg
March 28-April 9 Appomattox Campaign
April 2 Assault on and fall of Petersburg
April 3-9 Pursuit of Lee
April 6 Sailor’s Creek
April 9
Appomattox Court House

Surrender of Lee and his army.

April 23-27 March to Danville and duty there
May 23-June 3 March to Richmond, Va., then to Washington, D.C.
June 8 Corps Review
June 21 Mustered out