Joliet Army Ammunition Plant – Wilmington, Illinois - Atlas Obscura

Joliet Army Ammunition Plant

Wilmington, Illinois

This national park dedicated to the tallgrass prairie ecosystem still displays its military past.  

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About 19 miles southwest of Chicago near the city of Joliet resides a massive plot of restored prairie land. This is the former site of the Joliet Ammunition Plant, which produced TNT and artillery shells during World War II, the Korean War, and the Vietnam War. 

By the late 1970s, operations at the plant ceased. In 1993, the land was declared to be excess and a redevelopment project was planned. A portion of this new development included 19,000 acres of land that was handed over to the U.S. Forest Service. That land became part of the Midewin National Tallgrass Prairie, the first national park of its kind, followed by Tallgrass Prairie National Preserve in Kansas.

Today, the land is public property for all to enjoy. Visitors can still find traces of the park’s military history. The most notable of these is a field of concrete bunkers that were known as the “igloos” by factory workers. They were once used to store massive quantities of explosives and ordinance.

Although most of the bunkers are shuttered with heavy steel doors, others remain open for tourists. Inside, visitors will also find scattered graffiti that provide clues into the lives and jobs of the people who once worked inside. 

Know Before You Go

To see the bunkers, visitors should go to the Iron Bridge Trailhead and hike the Group 63 Trail, which is a 3.6-mile loop around all the bunkers. 

To reach the trailhead, go to The Midewin National Tallgrass Prairie Welcome Center and then follow these instructions:


  • Turn right/north onto Route 53

  • Travel north on Route 53 for 2.4 miles.

  • Turn right/east onto the gravel road to the parking area and trailhead