21st Cavalry Division (United States)
|21st Cavalry Division|
Shoulder Sleeve Insignia
|Branch||Army National Guard|
U.S. Cavalry Divisions
|15th Cavalry Division||22nd Cavalry Division|
The 21st Cavalry Division was a division of the United States Army National Guard located in the north eastern United States. The division was composed of personnel from the New York, New Jersey, Pennsylvania and Rhode Island Army National Guards.
The division was created from the perceived need for additional cavalry units after the First World War. It numbered in succession of the Regular Army Divisions, which were not all active at its creation.
The division was constituted in 1921 and assigned to the First Army. Not all authorized units were active during the division's lifetime. The division did not participate in the First Army maneuvers in 1935, 1939, and 1940. The 21st was inactivated on 1 October 1940 and disbanded on 1 November 1940.
- Headquarters, New York City, New York
- 51st Cavalry Brigade, New York 
- 59th Cavalry Brigade, Newark, New Jersey
- 112th Field Artillery Regiment, Trenton, New Jersey 
- Headquarters Special Troops, West New Brighton, New York
- United States Army branch insignia
- List of armored and cavalry regiments of the United States Army
- Headquarters Troop, 51st Cavalry Brigade Armory 
- New York Army National Guard Heraldry 
- U.S. Army Order of Battle 1919–1941, Volume 2. The Arms: Cavalry, Field Artillery, and Coast Artillery, 1919–41 by Lieutenant Colonel (Retired) Steven E. Clay, Combat Studies Institute Press, Fort Leavenworth, KS, 2011
- Maneuver and Firepower, The Evolution of Divisions and Separate Brigades, by John B. Wilson, Center of Military History, Washington D.C., 1998
- Cavalry Regiments of the U S Army by James A. Sawicki Wyvern Pubns; June 1985
- , The Trading Post, Journal of the American Society of Military Insignia Collectors, April- June 2009, pages 20 & 21