The 21st New York Cavalry Regiment lost 3 officers and 63 enlisted men killed and mortally wounded and 1 officer and 76 enlisted men to disease during the Civil War.

1863
Organized at Troy, N.Y.
August 28 Companies A, B, C & D mustered in
September 1 Company E mustered in
September 4 Companies A, B, C, D & E left State for Washington, D.C. and duty at Camp Stoneman, Defenses of Washington, D. C, attached to 22nd Army Corps, Dept. of Washington, D.C.
September 18 Company F mustered in
September 19 Company F left State for Washington, D.C.
October 14 Company G mustered in
October 15 Company H mustered in
October 16 Company I mustered in
October 19 Companies G, H and I left State for Washington D.C.
November Company K mustered in and left State for Washington D.C.
December Company L mustered in
1864
January Company M mustered in. Regiment attached to Cavalry Brigade, 1st Division, Army of West Virginia
January 4 Attempt to capture Lieutenant Washington by Company H. Company ambushed near Smithfield, Va.
January 22 Berryville Ford
January 23 Newtown and Woodstock
January 27-February 7 Operations in Hampshire and Hardy Counties, W. Va.
February Companies L & M left State for Washington D.C.
February 2 Mechanicsburg Gap
February 4 Moorefield
February 6-7 Moved to Harper’s Ferry, thence to Halltown, Va., Charlestown
February 14 Near Smithfield
February 20 Paris
April 10 Near Kablestown
April 24 Near Middletown (Detachment)
April 30-May 16 Sigel’s Expedition from Martinsburg to New Market. Attached to 1st Brigade, 1st Cavalry Division, Army of West Virginia
May 10 Brock’s Gap
May 15 Battle of New Market
May 21, 29 & 30 & June 3 Newtown
May 26-July 1 Hunter’s Raid on Lynchburg
June 5 Piedmont
June 6 Occupation of Staunton
June 14 Lexington
June 16 Otter Creek
June 17 Diamond Hill
June 17-18 Lynchburg
June 19 Liberty
June 21 Catawba Mountains
June 21-22 Salem
June 27 Bushy Ridge, Charlestown
July 1 Winchester
July 2 Bunker Hill
July 3 Buckton
July 4 Pleasant Valley
July 7 Solomon’s Gap
July 7 Brownsville
July 11 Frederick City
July 15-16 Near Hillsboro
July 16 Purcellsville and near Wood’s Grove
July 17-18 Snicker’s Gap and Snicker’s Ferry
July 19 Ashby’s Gap and Berry’s Ford
July 20 Salem
July 20 Stevenson’s Depot
July 23 Near Kernstown
July 24 Kernstown, Winchester
July 25 Bunker Hill and Martinsburg
August Attached to 2nd Brigade, 1st Cavalry Division, Army of West Virginia
August 21-22 Near Charlestown
August 24 Falling Waters
September Duty at Remount Camp, Cumberland, Md., Dept. of West Virginia
October 25-26 Milford
November Attached to 1st Brigade, 2nd Division, Cavalry Corps, Army of the Shenandoah, Middle Military Division
November 12 Nineyah
November 22 Stony Creek, Hawkinsville, and Rude’s Hill, near Front Royal
November 24 Near Kernstown
November 29 Near Winchester
December 4 Near Millwood
December 6 White Post
December 19-28 Raid on Gordonsville
December 21 Liberty Mills
December 22-23 Gordonsville
December 26 Warrenton
December 27 Ashby’s Gap
1865
January 19 Near Paris
February 18-19 Expedition from Winchester into Loudoun County
February 19 Ashby’s Gap
March Attached to Tibbitt’s Brigade, District of Harper’s Ferry, Dept. of West Virginia
March 22 White Post
April 9 Near Berryville
April-May Duty at Washington, D.C. Attached to 22nd Army Corps, Dept. of Washington
June Duty at Fort Leavenworth, Kansas attached to the Dept. of Missouri
September At Denver, Colo.
1866
June 23 Company B mustered out at Denver, Colo.
June 26 Company F mustered out
June 29 Company G mustered out
July 3 Company C mustered out
July 5 Company E mustered out
July 7 Company D mustered out
August 31 Company A mustered out at Fort Leavenworth, Kansas