Question: For which war was the ammunition plant, located in Illinois, and now a tallgrass prairie reserve; the largest conservation site in the Chicago Wilderness region, originally opened?
Sentence (from "Joliet Army Ammunition Plant"): Opened in 1940 during World War II, the facility consisted of the Elwood Ordnance Plant (EOP) and the Kankakee Ordnance Works (KNK).
Relevant evidence: Yes