On 3 March 1855, the US Army constituted its fourth regiment of mounted troops.
After the Mexican War and the various Indian wars against the Fox, Kickapoo, Dakota, and Sauk American Indians, the US Congress recognized a need for more regular mounted soldiers on the frontier. At the time the US had three mounted regiments: the 1st and 2nd Mounted Dragoons and the 1st Mounted Rifles. On 3 March 1855, the US constituted a fourth mounted regiment, the 1st Cavalry Regiment at Jefferson Barracks, Missouri under the command of Colonel Edwin Voss Sumner to augment the other troops on the frontier. After they were organized and training completed, the 1st Cavalry Regiment maintained law and order in the Kansas Territory and protect settlers from Indian attacks.
After the attack on Ft Sumter in 1861, the troopers and officers of the 1st Cavalry Regiment parted ways to fight on their respective sides during the US Civil War. 27 of those troopers became general officers during the war, including George C McClellan, Jeb Stuart, and Robert E. Lee, the commander of the regiment at the outbreak of the war.
Two months later, the US Army’s mounted regiments were re-designated by seniority. The 1st and 2nd Mounted Dragoons became the 1st and 2nd Cavalry Regiments, the 1st Mounted Rifles became the 3rd Cavalry Regiment, and the 1st US Cavalry Regiment became the 4th United States Cavalry Regiment.
Prepared and Loyal!