Apparently it was once a top-secret military base, part of the Stanley R Mickelsen Safeguard Complex, and was used among other things to store nuclear warheads during the Cold War. I've also read it was supposed to be some kind of bunker, and I've also read it was some kind of missile tracking system, and I've also read it was a radar device to track incoming missiles. Strange that many links say many different things...
Then after the Cold War, it was supposedly emptied and abandoned. For a short time in the 1980s the barrack buildings on the site were turned into a youth camp until the Reagan administration cut the funding.
Then, it was mysteriously bought by an odd pacifist sect called the HUTTERITES ( http://www.hutterites.org/ ), which from what I've read haven't done shit with it, aside from plant a few crops of soybeans and alfalfa at the land’s perimeter.
