The 203rd Coast Artillery was originally organized as the 2nd Infantry Regiment, Missouri National Guard, on 15 October 1890. Some of the companies of this regiment claimed descent from companies of the earlier 5th Missouri Infantry Regiment, organized on 26 November 1883 from companies originally formed as far back as 1876, and disbanded on 19 April 1887. On 12 May 1898, the 2nd Missouri Infantry was mustered into federal service for the
Spanish–American War and was mustered out from 27 February – 3 May 1899. The 2nd Missouri was reorganized in the Missouri National Guard in June 1899. It was mustered into service
on the Mexican border on 28 June 1916, and was mustered out on 17 January 1917. On 5 August 1917, the regiment was drafted into federal service after
American entry into World War I. National Guard units were formed into divisions, and the 2nd Missouri Infantry became part of the
35th Division, its elements being used to form different units. The Supply Company and Headquarters Company (less Band) formed the 110th Trench Mortar Battery. The 1st Battalion and the Machine Gun Company formed the 128th Machine Gun Battalion, the 2nd Battalion formed the 129th Machine Gun Battalion, and the 3rd Battalion formed the 130th Machine Gun Battalion. The Band was assigned to the 311th Cavalry Regiment. The 35th Division served overseas in France in the Meuse-Argonne, Alsace, and Lorraine Campaigns, and the former 2nd Missouri Infantry was mustered out of service in May 1919. The 2nd Artillery (Antiaircraft) was constituted in the Missouri National Guard on 28 April 1921 as from new and existing units as follows: • HHB from new • HHB 1st Battalion from new • Battery A from Company B, 128th Machine Gun Battalion • Battery B from Company B, 129th Machine Gun Battalion • Battery C from new • Battery D from Company B, 140th Infantry Regiment • HHB 2nd Battalion from new • Battery E from new • Battery F from Company B, 130th Machine Gun Battalion • Battery G from Company A, 130th Machine Gun Battalion The regimental headquarters was organized and federally recognized on 2 June 1921 at
Aurora, Missouri. On 1 October 1921, the regiment was redesignated as the 203rd Artillery Regiment (Antiaircraft), Coast Artillery Corps, and assigned to the
VII Corps. From 9 July to 5 August 1922, the 1st and 2nd Battalions performed riot control during a coal miners' strike at
Moberly and
Macon, Missouri. On 19 April 1924, the regiment was reorganized as the 203rd Coast Artillery Regiment (Antiaircraft). On 18 March 1933, the headquarters location changed to
Webb City, Missouri. On 1 October 1933, the regiment was relieved from the VII Corps and assigned to the General Headquarters Reserve. From 30 April to 4 May 1934, the 2nd Battalion performed riot control duty during a coal miners' strike at
Mindenmines, Missouri. The entire regiment was used for
flood control duty in southern Illinois from 21 January to 5 April 1937. Normal summer training usually took place at Camp Clark, near
Nevada, Missouri. Because of the lack of locations suitable for live firing of 3-inch antiaircraft guns and machine guns in Missouri, the regiment conducted such training at locations like
Camp Custer,
Michigan,
Fort Sill,
Oklahoma,
Fort Sheridan,
Illinois,
Camp Hulen,
Texas, and
Fort Barrancas,
Florida. The regiment participated in major field army maneuvers at
Fort Riley,
Kansas, and
Camp Ripley,
Minnesota, in 1937 and 1940. The regiment was inducted into federal service on 16 September 1940 and was assigned to the 33rd Coast Artillery Brigade (Antiaircraft). The 3rd Battalion was constituted on 27 May 1942 at
Fort McDowell,
California. The regiment was broken up on 12 February 1944 a and reorganized and redesignated as follows: • HHB as HHB, 203rd Antiaircraft Artillery Group (eventually redesignated HHD
35th Division Trains) • 1st Battalion as 86th Antiaircraft Artillery Gun Battalion • 2nd Battalion as 592nd Antiaircraft Artillery Automatic Weapons Battalion • 3rd Battalion as 299th Antiaircraft Searchlight Battalion Units redesignated in 1946 as follows: • 86th Battalion as 108th Mechanized Cavalry Reconnaissance Squadron (27 June 1946) • 592nd Battalion as 196th Tank Battalion (27 June 1946) • 299th Battalion as
175th Military Police Battalion (3 July 1946) The 108th Mechanized Cavalry Reconnaissance Squadron was redesignated 1 November 1949 as 203rd Antiaircraft Artillery Automatic Weapons Battalion (Mobile), reorganized and redesignated 1 December 1952 as 203rd Antiaircraft Artillery Gun Battalion. redesignated 1 October 1953 as 203rd Antiaircraft Artillery Battalion (90mm). • consolidated 15 April 1959 with 203rd Combat Arms Regiment, a parent regiment under the
Combat Arms Regimental System. This was part of the larger reorganization that placed the Army National Guard under the ROCID/
Pentomic organization. The battalion was redesignated 1st Reconnaissance Squadron, 203rd Combat Arms Regiment, and had its units remain in place at
Joplin,
Anderson,
Monett, and
Neosho. • redesignated 203rd Armor Regiment, 1963 • redesignated 203rd Engineer Battalion, 1968 ==Distinctive unit insignia==