The history of the 100th Regiment can be divided into two distinct periods. From its constitution in July 1918 as the HQ, 175th Field Artillery Brigade until its reorganization and redesignation in 1959, the 100th was no different than other regiments in the Artillery branch—it deployed during World War II, earned battle honors for three campaigns, and underwent its share of reorganizations and redesignations. After it became HQ and HQ Company, 100th Regiment, an element of the 100th Division (Training), however, it essentially became an administrative unit, with its battalions designated as elements in divisions where they would undergo training.
From 1959 until 2008, both the Regiment and its battalions were elements of the 100th Division (Training), but on 1 October 2008 seven of the regiment’s battalions were relieved from assignment to the 100th Division. In September 2009, the Regiment was reorganized so that its thirteen battalions were elements of three different Training Divisions: the 100th (3rd, 8th 11th, 12th Battalions), the 94th (5th, 6th, 7th, and 13th Battalions), and the 102nd (1st, 2nd, and 4th Battalions). (The number of Battalions and the Divisions to which they are assigned is not constant, however, and can be increased or decreased to meet the Army’s needs.)
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Commonly called a unit crest or DUI for short, the Distinctive Unit Insignia of the 100th Regiment was originally authorized for the 375th Field Artillery Regiment on 27 April 1933. It has been redesignated three times since then, starting in October 1942 for the 375th Field Artillery Battalion, in January 1950 for the 375th Parachute Field Artillery Battalion, and lastly in July 1960 for the 100th Regiment. Its shield denotes Artillery, the unit’s branch at the time it was designed. The horseshoe commemorates Virginia Lieutenant Governor Alexander Spotswood’s 1716 thirty-man exploratory expedition that crossed the mountains into what is now West Virginia; at its conclusion, the men were organized and designated as Knights of the Golden Horseshoe and presented with small golden horseshoes in recognition of the organization of the 175th Field Artillery Brigade in Parkersburg, West Virginia in 1921.
Full guidance on wear of the DUI is found in DA Pamphlet 670-1,
Section 21-22, "Distinctive unit insignia" and 21–3(d) and (e),
"Beret" and
"Garrison Cap," respectively.