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?
Context: Joliet Army Ammunition Plant (JOAAP, formerly known as the Joliet Arsenal) was a United States Army arsenal located in Will County, Illinois, near Elwood, Illinois, south of Joliet, Illinois.  Opened in 1940 during World War II, the facility consisted of the Elwood Ordnance Plant (EOP) and the Kankakee Ordnance Works (KNK).  In 1945, the two were deactivated and combined forming the Joliet Arsenal.  The plant was reactivated for the Korean War and renamed Joliet Army Ammunition Plant during the Vietnam War.  Production of TNT ended in 1976, and the major plant operations closed shortly after in the late 1970s.  The facility briefly revived an automated load-assemble-pack (LAP) artillery shell operation that was managed by the Honeywell Corporation during the Reagan administration in the 1980s before it was finally closed. The Osage Plains are a physiographic section of the larger Central Lowland province, which in turn is part of the larger Interior Plains physiographic division.  The area is sometimes called the Lower Plains, North Central Plains, and the Rolling Plains.  The Osage Plains, covering west-central Missouri, the southeastern third of Kansas, most of central Oklahoma, and extending into north-central Texas, is the southernmost of three tallgrass prairie physiographic areas.  It grades into savanna and woodland to the east and south, and into shorter mixed-grass prairie to the west.  The Osage Plains consist of three subregions.  The Osage Plains proper occupy the northeast segment.  Although sharply demarcated from the Ozark uplift, the Plains are nonetheless a transitional area across which the boundary between prairie and woodland has shifted over time.  In the central portion of the physiographic area lies the second subregion, the Flint Hills, commonly called "The Osage" in Oklahoma.  This large remnant core of native tallgrass prairie is a rocky rolling terrain that run from north to south across Kansas and extends into Oklahoma.  To the west and south of these hills are the Blackland Prairies and Cross Timbers.  This vegetatively complex region of intermixed prairie and scrubby juniper-mesquite woodland extends into north-central Texas.  Bluestem prairies and oak-dominated savannas and woodlands characterize the natural vegetation in the Cross Timbers.  Much of the area has been converted to agriculture, although expanses of oak forest and woodland are still scattered throughout the eastern portion of the subregion. Konza Prairie biosphere reserve is a biosphere reserve located in the Flint Hills region of north-eastern Kansas, approximately 10 km south of the city of Manhattan.  The Flint Hills are steep-sloped and overlain by shallow limestone soils unsuitable for cultivation.  This region contains the largest remaining area of tallgrass prairie in North America since the majority of the Konza Prairie and the surrounding landscape have not been ploughed. Nine Mile Prairie (named for its location 5 mi west and 4 mi north of downtown Lincoln) is a 230 acre tract of conserved tallgrass prairie in Lancaster County, Nebraska, United States.  Except for one small portion of it that was farmed as recently as the 1950s, Nine-Mile Prairie has never been plowed (some of the land has at times been grazed as recently as the 1960s).  As such, it is one of the largest areas of virgin tallgrass prairie in the state of Nebraska.  It has been listed on the National Register of Historic Places since 1986. Neotibicen dorsatus, colloquially called the bush cicada or grand western cicada is a species of large bodied annual cicada in the genus "Neotibicen".  Unique among other species of "Neotibicen", this species is almost exclusively associated with Eastern tallgrass prairies and the Great plains region of central North America.  Prior to the European penetration and settlement of the interior of North America, this was among the most widespread and abundant cicada species in the great plains region; inhabiting a sprawling geographic range.  Unfortunately, the extensive destruction of the North American tallgrass prairie for the purposes of agriculture, livestock grazing, and urbanization has precipitated the widespread decline of this species and fragmentation of its distribution.  In certain areas of dense urban development or agricultural activity in its former range, populations have been decimated and the cicada effectively extirpated.  In modern times, it exists in isolated prairie remnants scattered across the great plains.  Although generally listed as a least concern species by conservation groups, remaining relict populations should be monitored and conserved. Chicago Wilderness is a regional alliance of more than 250 different organizations that work together to improve the quality of life of the individuals and the many other species living in the Chicago (Illinois) area.  Through the restoration and sustenation of the biological diversity that once encompassed the lands, their fundamental objective, to preserve the naturally occurring lands and waters in that region, is being made a reality.  Through these activities, Chicago Wilderness played a major role in protecting and replenishing the naturally occurring ecosystems in the Chicago area as well as motivating people to become more aware and involved in the preservation of these lands and waters.  Chicago Wilderness had continued to blossom through the funding and donations of many sources including private contributions, the member organizations, and state and federal grants. The Manitoba Tall Grass Prairie Preserve is located in southeastern Manitoba near Gardenton and Vita, this is about 50 km south of Steinbach, Manitoba.  It is one of the last remaining stands of tallgrass prairie in Manitoba and is part of the Tallgrass Aspen Parkland conservation area in Manitoba and Minnesota.  Several groups and organizations help in land preservation in the Manitoba Tall Grass Prairie such as the Nature Conservancy of Canada, Nature Manitoba, Environment Canada, Manitoba Conservation and the Manitoba Habitat Heritage Corporation. Tallgrass Prairie National Preserve is a United States National Preserve located in the Flint Hills region of Kansas, north of Strong City.  The preserve protects a nationally significant example of the once vast tallgrass prairie ecosystem.  Of the 400,000 square miles (1,000,000 km) of tallgrass prairie that once covered the North American continent, less than 4% remains, primarily in the Flint Hills.  Since 2009, the preserve has been home to the growing Tallgrass Prairie bison herd. The Tallgrass Prairie Preserve, located in Osage County, Oklahoma near Foraker, Oklahoma, is owned and managed by The Nature Conservancy.  It is protected as the largest tract of remaining tallgrass prairie in the world.  The preserve contains 39000 acre owned by the Conservancy and another 6000 acre leased in what was the original tallgrass region of the Great Plains that stretched from Texas to Manitoba. The Midewin National Tallgrass Prairie (MNTP) is a tallgrass prairie reserve and United States National Grassland operated by the United States Forest Service.  The first national tallgrass prairie ever designated in the U.S. and the largest conservation site in the Chicago Wilderness region, it is located on the site of the former Joliet Army Ammunition Plant between the towns of Elwood, Manhattan and Wilmington in northeastern Illinois.
Answer: World War II