The 18th Massachusetts Infantry Regiment lost 9 officers and 114 enlisted men killed or mortally wounded and 2 officers and 127 enlisted men to disease in the Civil War. It is honored by a monument at Gettysburg.

1861
August 27 Organized at Readville and Boston and mustered in
August 28 Left State for Washington, D.C.; attached to Fort Corcoran, Defenses of Washington
September 26 At Hall’s Hill, Va. Assigned to Martindale’s Brigade, Porter’s Division, Army of the Potomac.
1862
March Assigned to 1st Brigade, 1st Division, 3rd Army Corps, Army of the Potomac
March 10-16 Advance on Manassas, Va.
March 16-23 Moved to Alexandria, then to Fortress Monroe
March 27 Reconnaissance to Great Bethel
April 5 Warwick Road
April 5-May 4 Siege of Yorktown
May Assigned to 1st Brigade, 1st Division, 5th Army Corps, Army of the Potomac
May 27 Battle of Hanover Court House
May 27-29 Operations about Hanover Court House
June 25-July 1 Seven days before Richmond
June 26-July 2 Operations about White House Landing
July – August 15 At Harrison’s Landing
August 15-28 Retreat from the Peninsula and movement to Centreville
August 25 Major Joseph Hayes promoted to lieutenant colonel
August 30 Battle of Bull Run
September 16-17
Battle of Antietam

Commanded by Lieutenant Colonel Joseph Hayes, the regiment was in support of artillery but was not engaged

 September 19 Shepherdstown Ford
September 20 Shepherdstown, W. Va.
September 21 –
October 30
At Sharpsburg
October 30-
November 19
Movement to Falmouth, Va.
December 12-15
Battle of Fredericksburg
December 29-30 Expedition to Richards and Ellis Fords
1863
January 20-24 “Mud March”
January – April 27 Duty at Falmouth
April 27-May 6 Chancellorsville Campaign
May 1-5
Battle of Chancellorsville
June 11-July 24 Gettysburg Campaign
June 21 Ashby’s Gap
July 1-3
Battle of Gettysburg

The regiment was commanded by Colonel Joseph Hays. It brought 281 men to the field, losing 1 killed, 23 wounded and 3 missing.

July 14 Williamsport, Md.
July 27 –
September 17
At Warrenton and Beverly Ford
September 17 –
October 11
At Culpeper
October 11-22 Bristoe Campaign
November 7-8 Advance to line of the Rappahannock
November 7 Rappahannock Station
November 26-
December 2
Mine Run Campaign
December – May At and near Brandy Station and Stevensburg
1864
March Assigned to 3rd Brigade, 1st Division, 5th Army Corps
May-June Campaign from the Rapidan to the James
May 5-7
Battle of the Wilderness
May 8 Laurel Hill
May 8-21 Battle of Spotsylvania Court House
May 12 Colonel Hayes promomted to brigadier general
May 12 Assault on the Salient
May 23-26 North Anna River
May 23 Jericho Ford
May 26-28 On line of the Pamunkey
May 28-31 Totopotomoy
June 1-12
Cold Harbor
June 1-3 Bethesda Church
June 16-18 First Assault on Petersburg
June 16 to
October 21
Siege of Petersburg
June 21-23 Weldon Railroad
July 20 Old members left front
September 2 Old members mustered out. Veterans and Recruits consolidated to a Battalion.
September 30-
October 2
Poplar Springs’ Church, Peeble’s Farm
October 21 Consolidated with 32nd Massachusetts Infantry