After the outbreak of the Spanish-American War in April 1898, St. Louis again contributed a battery of artillery volunteers, which was sent to Puerto Rico and was mustered out on 30 November 1898.
It was drafted into Federal service on 5 August 1917 after American entry into World War I, redesignated on 1 October 1917 as the 128th Field Artillery, and assigned to the 35th Division.
The regiment arrived at the port of Boston on the troopship SS Vedic on 22 April 1919 and was demobilized on 19 May at Fort Riley, Kansas.
Per the terms of the National Defense Act of 1920, the regiment was redesignated on 1 October 1921 as the 128th Field Artillery, and subsequently assigned to the General Headquarters Reserve.
The regiment was assigned on 1 October 1933 to the 25th Field Artillery Brigade (GHQR), and converted from portée to truck-drawn on 1 January 1935.
For at least two years, in 1939 and 1940, the regiment also trained twenty-nine battery-grade field artillery officers of the Organized Reserve's 102nd Division at Fort Sill and Camp Ripley, Minnesota.
[2] The 128th Field Artillery was inducted into federal service on 25 November 1940, prior to U.S. entry into World War II, and moved to Fort Jackson, South Carolina, where it arrived on 10 December 1940.
[3] After fighting in northern France, Belgium, Luxembourg, and Germany in 1944-1945, the battalion was inactivated on 27 November 1945 at Camp Kilmer, New Jersey, and relieved from assignment to the 6th Armored Division.