Of all the regiments in the United States Army in the Civi War the First Maine Heavy Artillery Regiment sustained the greatest loss in battle, losing 23 officers and 400 enlisted men killed and mortally wounded; 260 also died of disease, a total of 683.

The regiment is honored by a monument on the Petersburg battlefield, where it suffered the greatest single day’s loss in killed and mortally wounded of any regiment in the Civil War.

August 21 Organized at Bangor as 18th Infantry and mustered in
August 24 Left State for Washington, D.C.
August 26 Duty in the Defences of Washington, building and garrisoning batteries and forts. Eight Companies at Fort Alexandria, Company E at Batteries Vermont and Mattox, Company K at Batteries Cameron and Parrott.
January 6 Designation changed to 1st Heavy Artillery
February Attached to 2nd Brigade, Haskins’ Division, 22nd Army Corps. Defences North of the Potomac
January Company L organized
February Company M organized
May 15 Attached to 2nd Brigade, 4th Division, 2nd Army Corps, Army of the Potomac and Moved to Belle Plains, Va. as a part of Tyler’s Heavy Artillery Division.
May 18 Rapidan Campaign
May 24 Attached to 1st Brigade, 3rd Division, 2nd Army Corps
May 19
Harris’ Farm, Fredericksburg Road

The regiment lost 82 killed, 394 wounded, and 5 missing; total 481

May 20-23 On line of North Anna
May 23-26 North Anna
May 26-28 On line of the Pamunkey River
May 23-31 Totopotomoy
June 1-5
Cold Harbor
June 5-12 Barker’s Mills
June 16-19 Before Petersburg
June 18
Hare’s House, Assault on Petersburg

Sustained the greatest loss of any one Regiment in any one action of the war: 635 killed and wounded out of 900 engaged.

From the wayside marker on the Petersburg battlefield:

The field became a burning, seething, crashing, hissing hell, in which human courage, flesh and bone were struggling with an impossibility.…
– Capt. Horace H. Shaw, 1st Maine Heavy Artillery

At 4:30 p.m. on June 18, 1864, this regiment of former garrison troops charged across this field toward the Confederate lines near Colquitt’s Salient. As they moved, their supports — veteran regiments who knew the folly of attacking entrenched positions — huddled under cover, leaving the 1st Maine to attack alone. Confederate musketry and artillery devastated the regiment.

For the next ten minutes, the 1st Maine Heavy Artillery lost the equivalent of a man each second: 632 men killed and wounded (out of almost 900 engaged), more than any other regiment in any other single battle of the war. The Confederates, behind earthworks, lost just 25.

June 16 Siege of Petersburg
June 22-23 Weldon Railroad
June 24 – July 23 Picket duty at Deserted House
July Attached to 2nd Brigade, 3rd Division, 2nd Army Corps
July 27-29 Demonstration on north side of James River
July 27-28 Deep Bottom
July 29 –
August 12
Duty at Hare’s House
August 13-20 Demonstration on north side of James River
August 14-18 Strawberry Plains
August 19 Near Fort Sedgwick
September 30 –
October 2
Poplar Springs Church
October 1 Yellow House
October 2 Squirrel Level Road
October 6-24 At Fort Sedgwick
October 27-28 Boydton Plank Road, Hatcher’s Run
December 7-12 Warren’s Hicksford Raid
February 5-7 Hatcher’s Run
March 25 Armstrong House
March 28-April 9 Appomattox Campaign
March 29 South Side Railroad
March 29-31 Boydton Road and White Oak Ridge
April 2 Fall of Petersburg
April 5 Jettersvtlle
April 6 Amelia Springs and Sailor’s Creek
April 7 Farmville
April 9
Appomattox Court House

Surrender of Lee and his army.

May 9-16 Moved to Washington, D.C.
May 23 Grand Review
June Attached to 3rd Brigade, Hardin’s Division, 22nd Corps
June 27 Garrison Forts in the Defences of Washington from Fort Washington to Fort Mahone
September 11 Mustered out and ordered to Bangor, Me.
September 20 Discharged