I would love to know if this was found other than randomly poking around and if so how it worked specifically. "out of place shapes in the middle of fields" might find out some other neat stuff too.
https://www.google.com/maps/place/38%C2%B043'29.7%22N+93%C2%...
Granted I like aerospace engineering as a software engineer so I grew up knowing about it ahead of time, and it's only an hour and a half drive away.
https://www.google.com/maps?ll=38.730306,-93.547864&z=12&t=h...