The 2nd United States Cavalry Regiment lost 5 officers and 73 enlisted men killed or mortally wounded and 3 officers and 92 enlisted men to disease during the Civil War. The regiment is honored by a monument at Gettysburg.

In August of 1861 the regiment was renamed the 5th United States Cavalry when the  2nd United States Dragoons changed their name to the 2nd United States Cavalry.

 The “Old” 2nd United States Cavalry Regiment

See below in August 1861 for the renamed 2nd United States Regiment of Dragoons
1861
January At the beginning of the year the regiment was in Texas under the command of Lieutenant Colonel Robert E. Lee. The regiment’s colonel, Albert Sidney Johntson, was serving in California as Commander of the Department of the Pacific.
February Texas left the Union. General David Twiggs, Commander of the Department of Texas, surrendered all United States forces in the department. Arrangements were made for the 2nd Cavalry to be evacuated north, and Lieutenant Colonel Lee returned to Washington. When Colonel Johnston in California learned of the secession of Texas, which he considered his adopted home state, he resigned his commission.
February 21 Companies D under Captain I.N. Palmer and Company H under Captain Kenner Garrard evacuated Camp Cooper, Texas; Company I under Captain A.G. Brackett evacuated Camp Verde.
February 26 Company B under Major E. Kirby Smith evacuated Camp Colorado, Texas.
March Lieutenant Colonel Lee was appointed colonel of the 1st Cavalry but would never take up the command.
March 3 Major Edmund Kirby Smith resigned at San Antonio, dated April 6
March 15 Company K, under the command of Captain C.J. Whiting evacuated Camp Wood, Texas
March 17 Company E evacuated Camp Hudson, Texas
March 19 Company G under Captain George Stoneman was evacuated from Camp Colorado near Brownsville, Texas, to Pass Cavallo, Texas and Company C under Captain J. Oakes evacuated Fort Inge, Texas.
March 21 Captain W. R. Bradfute of Company G resigned. Lieutenant M.M. Kimmel took command of the company.
March 29 Companies A and F, commanded by Captain R W Johnson, evacuated Fort Mason, Texas
March 31-April 4 Companies B, D, E, G, H & I moved by steamship Coatzacoalcos from Pass Cavallo, Texas to Key West, Florida
April 4-11 Companies B, D, E, G, H & I moved by steamship Coatzacoalcos to Havana, Cuba and then on to New York City
April 12-13 Company D under Captain Innes Palmer, accompanied by company H, moved from New York to Washington.
Companies B, D, E, G & I under Major George Thomas were ordered to Carlisle barracks, Pennsylvania.
April 12-25 Companies A, C, F & K moved from Pass Cavallo, Texas on the steamship Empire City to Havana, Cuba and to New York City
April 25 The War Department accepted Albert Sidney Johnston’s resignation as colonel of the regiment, and Major George H. Thomas was promoted to Lieutenant Colonel.

Company A arrived in New York City from Texas.

April 27-28 Companies A, C, F & K moved to Carlisle Barracks, Pennsylvania
April 14 Company D was stationed opposite the War Department in Washington.
May 3 Lieutenant Colonel Thomas was promoted to colonel and
May 6-10 Companies B, E, G & I moved to Washington via York, Pennsylvania and Brookeville, Maryland. Companies B, G & I stationed at the Park Hotel on 7th Street assigned. They were assigned to guard duty at the White House and Treasury Building. Company E under 1st Lieutenant J.J. Sweet was stationed in Alexandria, Virginia and assigned as escort to Colonel Samuel P. Heintzelman, Commanding the Third Division, Army of Northeastern Virginia.
May 22 Captain C. W. Field of Company B resigned. Captain George Stoneman of Company E was transferred to the 1st Cavalry as major and Captain J. Oakes of Company C was appointed major.
May 26 Occupation of Arlington Heights, Virginia. Company G under the command of Lieutenant T. Drummond crossed the Potomac via the Long Bridge. It joined Company I under Captain A.G. Brackett at Arlington House, who were assigned as escort to Brigadier General McDowell.
June 1 Skirmish at Fairfax Court House (Company B)
June 10 Colonel Thomas was assigned to command of  the 1st Brigade, 1st Division, Patterson’s Army. Companies A, C F & K were attached to the brigade
June 15 Companies A, C F & K advanced from Greencastle, Pennsylvania via Hagerstown to Williamsport, Maryland.
June 20 Company B at Ball’s Crossroads
July 2
Falling Waters

Companies A, C F & K crossed the Potomac and were engaged in the skirmish on Porterfield’s Farm without casualties. Afterwards the advance continued to Hoke Run.

July 3 Companies A, C F & K advanced along the Valley Pike to Martinsburg
July 15 Companies A, C F & K moved to Bunker Hill
July 16-21 Advance on Manassas, Virginia by companies B, E, G & I attached to Major Innes Palmer’s Battalion of United States Cavalry in Colonel Andrew Porter’s 1st Brigade of Hunter’s 2nd Division, Department of Northeastern Virginia
July 18 Blackburn’s Ford
July 21 Companies A, C F & K moved to Harpers Ferry
July 21
Battle of Bull Run
August Companies A, C F & K assigned to 1st Brigade, Banks’ Division, Shenandoah
August 3 The regiment’s designation was changed to Fifth United States Cavalry Regiment

 The “New” 2nd United States Cavalry Regiment

Formerly the 2nd United States Regiment of Dragoons
August 3 The 2nd Regiment of Dragoons was redesignated the Second Cavalry Regiment. 
August 13 Captan F.C. Armstrong of Company F resigned.
August 17 Assigned to Cavalry Reserve, Army Potomac
December All Companies in Washington. D.C. except C, G & I
1862
March Assigned to Provost Guard, Army Potomac
April – August Peninsula Campaign
April 5-May 4 Siege of Yorktown, Va.
May 23 Ellison’s Mill near Mechanicsville (Detachment)
May 24 New Bridge (Detachment)
June 25-July 1 Seven days before Richmond
October 16-17 Reconnaissance to Charlestown, W. Va.
October 16 Charlestown
November 23 Companies G & I arrived Washington, D.C.
December 29-30 Expedition from Potomac Creek to Richards and Ellis Fords, Rappahannock River
1863
January 13 Companies G & I joined Regiment at Falmouth, Va.
February Attached to Reserve Brigade, 1st Division, Cavalry Corps, Army Potomac
April 27-May 8 Chancellorsville Campaign
April 29-May 8 Stoneman’s Raid
May Company C joined Regiment at Falmouth, Va.
June 9
Battle of Brandy Station

Commanded by Captain Wesley Merritt.

June 11-21 Expedition from Point Lookout, Md., to Pope’s Creek (Detachment)
June 19 Middleburg
June 21 Upperville
June 29 Captain Merritt was promoted to brigadier general. Captain Theo. F. Rodenbough took over the regiment.
July 1-3
Battle of Gettysburg

The regiment was commanded by Captain Theo. F. Rodenbough.

From the monument at Gettysburg:

July 3. Moved with the Brigade at 12 m. under Brig. General W. Merritt from Emmitsburg and attacked the Confederate right and rear and was engaged for four hours until the action was brought to a close by a heavy rain.

Casualties: killed 3 men wounded 1 officer and 6 men missing 1 officer and 8 men.

July 6 Williamsport, Md.
July 10-13 Boonesboro
July 14 Falling Waters
July 21-22 Manassas Gap
July 23 Wapping Heights
July 31-August 1 Kelly’s Ford
August 1-4 Brandy Station
September 13-17 Advance from the Rappahannock to the Rapidan
October 9-22 Bristoe Campaign
October 17 Manassas Junction
October 18 Bristoe Station
November 7-8 Advance to line of the Rappahannock
November 26-December 2 Mine Run Campaign
1864
February 6-7 Demonstration on the Rapidan, Barnett’s Ford
February 28-March 1 Custer’s Raid in Albemarle County
February 29 Near Charlottesville
March 1 Stannardsville
May 4-June 12 Rapidan Campaign
May 5-7 Wilderness
May 7-8 Todd’s Tavern
May 9-24 Sheridan’s Raid to the James River
May 11 Ground Squirrel Church and Yellow Tavern
May 12 Mechanicsville
May 26-28 Line of the Pamunkey
May 27 Hanovertown Ferry and Hanovertown
May 28 Haw’s Shop
May 28-31 Totopotomoy
May 30 Old Church and Mattadequin Creek
May 31-June 1 Bethesda Church, Cold Harbor
June 7-24 Sheridan’s Trevillian Raid
June 11-12 Trevillian Station
June 12 Mallory’s Cross Roads
June 21 Black Creek or Tunstall Station and White House or St. Peter’s Church .
June 23 Jones’ Bridge
July Siege of Petersburg
July 27-28 Deep Bottom
July 28 Malvern Hill
August 7-
November 28
Sheridan’s Shenandoah Valley Campaign. Attached to 3rd (Reserve) Brigade, 1st Division, Cavalry Corps, Army Shenandoah, Middle Military Division
August 11 Tell Gate near White Post and near Newtown
August 14 Near Strasburg
August 25 Halltown and near Kearneysville
August 28 Leetown and Smithville, Smithfield Crossing, Opequan
September 13 Locke’s Ford, Opequan Creek
September 15 Sevier’s Ford, Opequan Creek
September 19
Third Battle of Winchester (Opequan)
September 21
Fisher’s Hill
September 22 Milford
September 23 Front Royal
September 24 Luray Valley
September 25 Front Royal
September 26-27 Port Republic
September 28 Rockfish Gap
October 2 Mt. Crawford
October 8-9 Tom’s Brook, Woodstock Races
October 19
Battle of Cedar Creek
November 11 Near Kernstown
November 28-December 3 Expedition into Loudoun and Faquier Counties
December 19-28 Expedition from Winchester to near Gordonsville
December 22 Liberty Mills
December 23 Near Gordonsville
December Duty in the Shenandoah Valley until July, 1865.
1865
March Assigned to Cavalry Brigade, Army Shenandoah