The 120th Field Artillery Regiment was organized on 22 September 1917 at Camp MacArthur, as a part of the 57th Field Artillery Brigade, better known as the "Iron Brigade". The nickname originated with the 1st Wisconsin Cavalry and was traditionally given to crack artillery units in the Civil War. Once at Camp MacArthur, the division was resupplied for their overseas assignment. Shortly before the division left for France, 4,000 National Army troops from Wisconsin and Michigan were transferred to the division.