On 2 February 1901, Congress authorized the organization of the Twelfth Regiment of Cavalry, Army of the United States. Under this authority, the regiment was formed at Fort Sam Houston, Texas on 8 February 1901.
From 1901 until 1911, the Regiment served posts in Texas, Georgia, and the Philippines.
During World War II the 12th Cavalry served as an infantry regiment within the 1st Cavalry Division.
The regiment was deactivated prior to the 1st Cavalry Division's service in the Korean War, but its lineage was resurrected in with the creation in 1957 of the Combat Arms Regimental System, in which the battalions listed below were created.
After Operation Iraqi Freedom II, the 12th Cavalry Regiment underwent a major transition as elements from 2/7CAV, 1/9CAV, and 3/8CAV were reflagged and combined with the Regiment to create the battalions currently in operation. The 2nd Battalion, Twelfth Cavalry Regiment, as well as 2/7CAV and 1/9CAV moved to the 4th Brigade of the 1st Cavalry Division, and are currently operating from Fort Hood, Texas. The 1st Battalion, Twelfth Cavalry Regiment as well as 3/8CAV continue to operate at Fort Hood, Texas, and are now with the 3rd Brigade, and 2nd Battalion, Twelfth Cavalry Regiment now with 1st Brigade, both of them under the 1st Cavalry Division.