The 12th Pennsylvania Volunteer Cavalry Regiment lost 2 officers and 32 enlisted men killed or mortally wounded and 1 officer and 107 enlisted men to disease during the Civil War. It is honored by a monument at Antietam.

1861
December – April 1862 Organized at Philadelphia under Colonel William Frishmuth
1862
April Ordered to Washington, D.C.
April Duty at Washington, D.C. Attached to Military District of Washington
April 20 Colonel Frishmuth resigned. Lewis B. Pierce was promoted to colonel.
June 20 Moved to Manassas Junction, Va., and guard Orange & Alexandria Railroad
August Moved to Bristoe, thence to Alexandria, and picket north bank Potomac from Chain Bridge to Edward’s Ferry
September-October Maryland Campaign. Assigned to 4th Brigade, Pleasanton’s Cavalry Division, Army Potomac
September 12 Frederick, Md.
September 16-17
Battle of Antietam
October Duty on line of the Baltimore & Ohio Railroad, Headquarters at Sir John!s Run and Bath. Assigned to Averill’s Cavalry Command, 8th Army Corps, Middle Department
November Attached to Defenses Upper Potomac, 8th Corps
November 6 To Martinsburg, W. Va.
November 9 To Moorefield
November 24 To Newtown
December 26 To Kearneysville
1863
January 1 Bunker Hill
February Assigned to 1st Brigade, 2nd Division, 8th Corps
February 12 Near Smithfield and Charlestown
April 8 MillWood Road near Winchester
April 20 Reconnaissance from Winchester to Wardensville and Strasburg
April 22-29 Operations in Shenandoah Valley
April 22 Strasburg Road, Fisher’s Hill
April 25-30 Scout to Strasburg
June 12 Cedarville and Winchester
June 13-15 Winchester
June Attached to Pierce’s Brigade, Dept. of the Susquehanna
June 24 McConnellsburg, Pa.
July 5 Cunningham’s Cross Roads
July 5 Greencastle, Pa. (Detachment)
July 10 Near Clear Springs, Md.
July Attached to McReynold’s Command, Dept. Susquehanna
August 3 Moved to Sharpsburg, Md., then to Martinsburg. Attached to Martinsburg, W. Va., Dept. West Virginia
October 10 Jeffersonton, Va.
October Attached to 3rd Brigade, 1st Division, Dept. West Virginia
1864
February Attached to Reserve Division, Dept. West Virginia
February 5 Near Winchester
February 6 Middletown
April 26 Winchester
June 9 Affair in Loudoun County (Detachment)
June 29 Charlestown and Duffield Station
July 2 Bolivar Heights
July Attached to 1st Brigade, 1st Cavalry Division, West Virginia
July 15-16 Near Hillsboro
July 17 Charlestown
July 17-18 Snicker’s Ferry
July 19 Ashby’s Gap and Berry’s Ford
July 23 Near Kernstown
July 24 Winchester
July 25 Bunker Hill and Martinsburg
July 28 Cherry Run
July 29 Winchester
August Guard and garrison duty at Charlestown, covering railroad from Harper’s Ferry to Winchester. Attached to Reserve Division, Dept. West Virginia
September 27 Charlestown
November 12 Halltown and Mount Zion Church
November 24 Newtown
November 29 Charlestown (Detachment)
December 15 Colonel Pierce was discharged.
1865
January Attached to 3rd Infantry Division, West Virginia
January 1 Lieutenant Colonel Marcus A. Reno was transferred from a staff position, promoted to colonel and given command of the Regiment.
February 3 Affair at Harper’s Ferry (Detachment)
March 20-23 Scout from Harper’s Ferry into Loudoun County
March 21 Near Hamilton
March 23 Goose Creek
April Duty at Winchester and in the Shenandoah Valley attached to Cavalry, Army Shenandoah
July 20 Mustered out