Midewin is the first national tallgrass prairie in the U.S and one of the largest prairie restoration efforts east of the Mississippi River. It was established in 1996 on the site of what was once a sprawling military ammunition and explosives plant dating back to World War II. To restore the complex of wetlands that makes up the prairie, workers are dismantling hundreds of old grass-covered military bunkers, ripping up roadways and railroad lines and trying to strip out invasive weeds.