Before the Refuge existed, this area was the site of wartime industry. During World War II, the Department of War established the Illinois Ordnance Plant here because of its geographic location and the water supply at Crab Orchard Lake. Because explosives were the main product, different areas of the plant were isolated within what is now the sanctuary portion of Crab Orchard Refuge. At its wartime peak, the plant employed 10,000 workers and produced 425,000 shells and 70,150 bombs each month. The Congressional Act that established the Refuge in 1947 required that the wartime activities and facilities be converted into private industry, and this site became home to one of several companies carrying out that mandate while keeping industrial activity as compatible as possible with the needs of wildlife.