TNT was manufactured at the Joliet Army Ammunition Plant until 1976.
The rinse water from the manufacture of TNT is known as red water and is a significant pollutant and waste product.
TNT is one of the most commonly used explosives for military and industrial applications. It is valued partly because of its insensitivity to shock and friction, which reduces the risk of accidental detonation, compared to other more sensitive high explosives such as nitroglycerin.
TNT is poisonous, and skin contact can cause skin irritation, causing the skin to turn a bright yellow-orange color. During the First World War, munition workers who handled the chemical found that their skin turned bright yellow, which resulted in their acquiring the nickname "canary girls" or simply "canaries."
Bunkers or igloos at Midewin were used to store various products for the army including TNT
The Group 65 igloos were 80 feet long and were used to store smokeless powder (the propellant for shells).
Igloos in Groups 66, 66A and 68 were 60 feet long. Groups 66 & 66A were used to store "finished ammunition." Group 68 was used to store fuzes, primers and boosters, after assembly in Groups 4 & 5 and 8 & 9. The structures were sometimes referred to as "storage magazines" as well as "igloos.”
Group 63, where there is an interpretive sign near igloo 63-1, had 78 igloos, 40 feet in length. These were "high explosive" igloos. The group was serviced by a rail line running from the Manufacturing side, over what was then Route 66, on the "iron bridge.” It appears that TNT was brought from the Manufacturing side after being "cured", and stored in Group 63 until needed by the LAP (Load, Assemble and Pack) lines. A rail line exited this group and headed over to the four LAP lines (Groups 1, 3A, 2 and 3).
The igloos on the west side were all in Group 811 and were supplied with a vent shaft and ventilator. Here is where the newly-produced TNT was stored to cure.
Production of muntions at what is now Midewin caused some of the land to become comtaminated and remediation is an on-going process.
Thanks to www.fs.fed.us for the above.
Go find an ammo can. FTF pin waiting.
CONGRATS to superior o on the FTF. 
This is kind of a freaky area when the wind is roaring through the trees.