The 12th Division was an infantry division of the United States Army, active in 1918-1919. Established at Camp Devens, Massachusetts, training was interrupted by the World War I Armistice and the division was quickly afterwards disestablished.
The division was organized on July 12, 1918. The Regular 36th Infantry and 42d Infantry were ordered to Camp Devens in the latter part of July to become part of the 12th Division. (The 42nd Infantry had been assigned to the division on 5 July 1918). A certain number of non-commissioned officers and privates was taken from each company of the two regiments and assigned to the 73rd Infantry and 74th, both war-raised National Army, as a nucleus. The 12th Field Artillery Brigade, which was to become the divisional artillery, was organized and trained at Camp McClellan, Ala. It never actually joined the division at Camp Devens. It consisted of the 34th, 35th, and 36th Field Artillery Regiments and a trench mortar battery. By 1 September 1918 the training of the division for overseas service was well under way. Only after the Armistice of 11 November 1918 did orders arrive for the demobilization of the division. By 31 January 1919, all non-Regular commissioned and enlisted personnel had been discharged.
Major-General Henry P. McCain commanded this division from the time of its organization until it was demobilized. McCain remained in command of Camp Devens after the division was disestablished.