Battery E of the First Field Artillery of the Illinois National Guard was organized at Chicago, October 23, 1915, Captain Henry J. Reilly in command. On June 27, 1916, it was mustered into federal service for duty on the Mexican border, and mustered out October 28, 1916, after training at Leon Springs, Arkansas, and taking part in the famous "Austin Hike." The battery met for drill at the Dexter Pavilion, Union Stock Yards, Chicago, on Monday nights. After the United States declared war, April 6, 1917, the battery began recruiting to bring its strength up to war basis, and drilled Monday and Friday evenings. Sergeants Herman Leprohon and Thomas Atkinson, of the Regular Army, who directed the drill at this time, were commissioned first lieutenants in the regiment before it left Chicago. May 22 Paul E. Landrus was appointed First Sergeant, John J. O'Meara, Supply Sergeant, and F. O. Johnson, Stable Sergeant. Governor Lowden ordered the battery into service June 30, 1917, when drill became daily. July 9, the battery entrained for Fort Sheridan with its 30 horses, guns, caissons and supplies. First Lieutenant Irving Odell was in command, Captain Reilly having become colonel of the regiment, now the 149th U. S. Field Artillery. The regiment was mustered into federal service July 20, as part of the 67th F. A. Brigade and of the 42d Division, already named the Rainbow Division by Secretary of War Baker because of its national composition, comprising units of twenty-six states. At Camp Geismar, as Colonel Reilly named the regiment's encampment alongside Fort Sheridan, there was daily drill with the American 3-inch pieces. On July 30 the regiment was reviewed by General Berry, who was inspecting units of the 42d Division. Some of the "border veterans" of the battery had gone to the first Reserve Officers' Training Camp, and about twenty-five former members of Battery E received commissions. On September 3, 1917, the regiment left Chicago for Camp Mills, First Lieutenant Howard R. Stone in command, Captain Odell having been transferred to Second Battalion headquarters as captain-adjutant. Sergeant John Cowan and Corporal Russel Royer had shortly before been commissioned second lieutenants, the former remaining in the battery and the latter going to Headquarters Company. September 7, 1917, First Lieutenant Lawrence B. Robbins was transferred from Battery C to the command of Battery E, and shortly afterwards commissioned captain. Having no horses or guns, the regiment received plenty of foot drill, relieved by short periods of setting-up exercises, trigger-squeeze pistol practice and instruction in first aid to the wounded. The foot drill became hikes through Garden City and vicinity, then regimental reviews, and finally exhibited the accomplishment of the men in reviews by Secretary of War Baker and Major-General Mann.