We have a John Deere plant here in my hometown of Ankeny, Iowa. During WW2, it was used to make ordnance. Rumor has it there is tons of leftover ordnance buried underground on the property. The factory has been expanded many times since the war, had much of it's land used as a test bed for farming, and recently a lrage junk was sold to a large development company for a new housing project. According to a local paper, when the land was sold to the development company, haz mat teams surveyed the land for months, I would guess to locate any lost stores.