The 104th Cavalry Regiment wasn't actually raised until 1975 although some of its subordinate troops can trace their lineage back to the Revolutionary War. For example, Troop A, 1st Squadron, is also known as the First Troop Philadelphia City Cavalry, the oldest mounted unit in the U.S.
The 104th Cavalry has gone through many configurations, its elements serving as the 1st Pennsylvania Cavalry and the 8th Pennsylvania Infantry on Puerto Rico during the Spanish–American War.
On July 6, 1916, subordinate units of the regiment was mustered into Federal service for the Mexican border and stationed at El Paso, TX. The unit was mustered out on 22 January 1917.
On July 15, 1917, the regiment was drafted and mustered into Federal service for World War I as the 103rd Headquarters Troop, 28th Division; and on December 9, 1917, as 103rd Trench Mortar Battery, 53rd Field Artillery, 28th Division. It served in both France and Belgium and was mustered out on April 12, 1919, returning to state service with its headquarters at Harrisburg.
During WW2, the regiment was redesignated the 104th Cavalry Reconnaissance Squadron (Mechanized) and assigned to the 28th Infantry Division.
On August 25, 1952, the regiment was redesignated the 104th Armored Cavalry Regiment; on June 1, 1959, it was redesignated as the 1st Reconnaissance Squadron, 103rd Armor; on April 1, 1963, the 1st Reconnaissance Squadron, 223rd Cavalry; and finally, on 1 April 1, 1975, as the 1st Squadron, 104th Cavalry, headquartered in Philadelphia, PA.
In 1980, elements of the 104th Cavalry were used as extras in the George C. Scott film Taps (film).
On May 31, 2002, elements of the 1st Squadron, 104th Cavalry Regiment were mustered into Federal service as Task Force Saber. TF Saber deployed to Bosnia Herzegovina as a part of SFOR 12 for a NATO peacekeeping mission.
In 2003, the 2nd Squadron was reformed and the regiment's current configuration in the Pennsylvania Army National Guard is in two squadrons, one armored (1st) and one Stryker (2nd). While the 1st Squadron provided forces for peacekeeping operations in Bosnia and the Sinai, the 2nd Squadron deployed to Iraq in 2009.
As of 2012, the 1st Squadron is assigned to the 55th (Armor) Brigade, 28th Infantry Division and the 2nd Squadron is assigned to the 56th (Stryker) Brigade, 28th Infantry Division, Pennsylvania Army National Guard. As with most other Army units, there is no regimental headquarters, although a ceremonial regimental dining in is held annually at First City Cavalry's beloved armory in Philadelphia.