Each artillery battalion had three batteries. In the Artillery battalions, a battery consisted of four guns. One gun in a battery was designated the "base piece". It would fire the first shot in an engagement and the adjacent three would adjust their aim from readings of the base cannon.

123rd Field Artillery Regiment traces its lineage to the 6th Infantry Regiment which was constituted on 4 May 1882 in the Illinois National Guard and organized by re-designation of existing companies, which were organized in 1872-1878 in northwestern Illinois (Rock Island, Moline, Monmouth, Galesburg, etc). The unit was mustered into Federal service on 11 May 1898 as 6th Regiment, Illinois Volunteer Infantry and mustered out of Federal service on 25 November 1898 at Springfield, IL, and reorganized in 1903 in the Illinois National Guard as 6th Infantry.

It was mustered into Federal service on 25 April 1917; and drafted into Federal service on 5 August 1917. It converted and was re-designated on 19 September 1917 as the 123rd Field Artillery, and assigned to the 33rd Division. The unit demobilized on 9 June 1919 at Camp Grant, Illinois Army National Guard.

It was reorganized on 17 August 1921 at Galesburg and Monmouth as the 1st Battalion, 123rd Field Artillery, an element of the 33rd Division. It was expanded and re-designated on 3 June 1936 as 123rd Field Artillery, to consist of 3 battalions. It reorganized in 1940 by consolidation of elements to consist of 1st and 2nd Battalions, with batteries of the 1st Battalion at Rock Island, Galesburg, and Moline, and batteries of the 2nd Battalion at East St. Louis, Macomb and Alton. It was inducted into Federal service on 5 March 1941 at home stations.

The 123rd Field Artillery was broken up in 1942 and its elements reorganized and re-designated as follows:

• Headquarters and Headquarters Battery was re-designated on 12 February 1942 as Headquarters and Headquarters Battery, 208th Field Artillery, and relieved from assignment to 33rd Division
• 1st Battalion was re-designated on 12 February 1942 as 123rd Field Artillery Battalion; it remained assigned to the 33rd Division (subsequently 33rd Infantry Division)
• 2nd Battalion was re-designated on 18 April 1942 as 2nd Battalion, 200th Field Artillery, concurrently relieved from assignment to the 33rd Division and assigned to Task Force 6814 (later Americal Division)

After 1942, the elements underwent changes as follows:

• Headquarters and Headquarters Battery, 208th Field Artillery was re-designated 1 March 1943 as Headquarters and Headquarters Battery, 208th Field Artillery Group. It inactivated on 27 November 1945 at Camp Shanks, NY. Headquarters Battery, 208th Field Artillery Group was reorganized, re-designated and Federally recognized on 17 December 1946 as Headquarters and Headquarters Battery, 44th Division Artillery at Monmouth. It was released from active Federal service and reverted to State control on 10 October 1954. It was concurrently relieved from assignment to the 44th Infantry Division, consolidated with Headquarters and Headquarters Battery and Service Battery, 210th Field Artillery Battalion (organized and Federally recognized 1 March 1954 at Monmouth), and the consolidated unit designated as Headquarters and Headquarters Battery and Service Battery, 210th Field Artillery Battalion, an element of the 33rd Infantry Division.
• The 123rd Field Artillery Battalion inactivated 5 February 1946 in Japan. It was relieved on 5 July 1946 from assignment to 33rd Infantry Division and assigned to 44th Infantry Division. It was expanded, reorganized, and Federally recognized on 10 April 1947 as the 123rd Field Artillery Battalion, with elements at Galesburg, Monmouth, Aledo and Galva, and on 4 February 1947 as 223rd Field Artillery Battalion, with elements at Rock Island and Moline (both battalions assigned to 44th Infantry Division). The 123rd and 223rd Field Artillery Battalions were ordered into active Federal service on 15 February 1952 at home stations. It was released from active Federal service and reverted to State control on 10 October 1954. It was concurrently relieved from assignment to the 44th Infantry Division and the 223rd Field Artillery Battalion concurrently consolidated with the 133rd Antiaircraft Artillery Battalion, (organized and Federally recognized on 1 March 1954 with Headquarters at Rock Island), and the consolidated unit was designated as the 133rd Antiaircraft Artillery Battalion, an element of the 33rd Infantry Division. The 123rd Field Artillery Battalion consolidated on 1 December 1954 with the 209th Field Artillery Battalion (released from active Federal service and reverted to State control on 10 October 1954) and the 210th Field Artillery Battalion (organized and Federally recognized on 1 March 1954 with Headquarters at Monmouth); with the consolidated unit designated as the 123rd Field Artillery Battalion and assigned to 33rd Infantry Division.