This is one part of a series on the Indiana Army Ammunition Plant, covering the history of the plant pre-World War II and through the war.

The Indiana Army Ammunition Plant (IAAP) was spurred by the passage of the first National Defense Appropriations Act. Four days later, the Munitions Program was passed, in which the U.S. Ordinance Department sponsored private manufacturing corporations to design and produce ammunitions factories, producing smokeless gunpowder and other ordinances.

Speculation led up to the selection of the Indiana site as the potential home of an ammunitions factory. The Louisville Courier-Journal announced in July 1940 that the world’s largest smokeless powder plant would be constructed on the site of pioneer cemeteries, historic houses, homesteads and churches, and the former Rose Island Amusement Park that featured little resistance from those affected. The owners of the land accepted that the loss of their properties was a sacrifice to the foreseeable cost of war. The facility would be the largest plant in the Industrial Operations Command, containing 1,401 structures on 9,790 acres, although the figure would total much larger.

Constructed on 19,200 acres, INAAP included the Indiana Ordnance Works Plant 1 (IOW1) that produced smokeless powder, the Hoosier Ordnance Plant (HOP), also referred to as the “bag plant,” and the Indiana Ordnance Works Plant 2 (IOW2) that was referred to as the “rocket plant.”

Construction began on August 26, 1940 under E.I. du Pont de Nemours & Co., and just three months later, over 10,000 workers had been employed in the building of IOW1. At the height of construction in May 1941, there were 27,520 workers employed in the building of the plant. IOW1 was completed in May 1942.

IOW1 contained 800 buildings that were divided into four main areas. The administration area included a main administration building, telephone exchange, hospital, repair ship, cafeteria, guard headquarters and office space. The smokeless powder manufacturing area included six parallel, nearly identical manufacturing lines that included two power plants, blending towers, two Ammonium Oxidation plants, and two Nitric and Sulfuric Acid Concentration plants. Further south was the storage and shipping area that included approximately 100 above ground magazines, road ship houses and road storage and shipping houses. Towards the Ohio River was River Ridge, a collection of 19, two-story, wood-frame houses.

On January 10, 1941, construction began on the Hoosier Ordnance Plant (HOP) and was partially in operation by September; construction was finished on February 2, 1942. The load, assembly and pack facility was used to prepare cannon, artillery and mortar projectiles and integrated five distinct areas. The administration area included a main administration building, a main change house and a hospital, and the production, maintenance and storage area contained a bag manufacturing building, inert stores warehouse, a repair shop, a fire station and a heating plant. A charging area contained 8 load lines for bag loading smokeless powder and 4 igniter lines for bag loading black powder, whereas the powder magazine area contained 177 earth-covered, steel-reinforced concrete igloos. At River Ridge, an additional 17 two-story wood-frame houses were constructed.

Construction on Indiana Ordnance Works Plant 2 (IOW2), a rocket propellant plant, did not begin until late 1944. Although production did take place for approximately five weeks, the plant was never completed before the surrender of Japan in August 1945. Construction stopped on August 13.

In total, the Indiana Army Ammunition Plant contained 19,200 acres, 1,700 buildings, 84-miles of railroad track, 190 miles of road and 30 miles of fence and cost $133.4 million to complete.

IOW1 began producing smokeless powder and black powder to HOP and other load, assembly and pack operations on April 11, 1941. Single-base smokeless powder was used as a propellant for a projectile, while black powder was used to ignite the smokeless powder. By July, IOW1 had produced twice as much powder as the entire nation had the previous year.

Below are photographs depicting some of the history of INAAP and of the HOP and IOW2.