The 4th United States Cavalry Regiment lost 3 officers and 59 enlisted men killed and mortally wounded and 1 officer and 108 enlisted men to disease during the Civil War.

1861
Originally designated as 1st United States Cavalry Regiment. (see 1861 service as 1st Cavalry Regiment) Most of the regiment was in the Western Theater, but Companies A and E moved to the Eastern Theater. Company A was under the command of First Lieutenant Thomas H. McCormack and Company E under the command of Captain James B. McIntyre (USMA ’53), who was in overall command of the detachment.
August 3 Redesignated as 4th United States Cavalry. Companies A and E attached to Headquarters, Army of the Potomac
1862
April – August Peninsula Campaign
April 5-May 4 Siege of Yorktown
June 25-July 1 Seven days before Richmond
June 27 Gaines’ Mill
July 1 Malvern Hill
September 6-22 Maryland Campaign
September 16-17
Battle of Antietam
November Joined Regiment in Tennessee, 1862.