At the left and right edges are the two remaining "typical American Homes" from the Apple II Civil Defense test. A 29Kt device was detonated 500ft above the ground. The two structures at center are seismic test structures (erected more than 10 years after Apple II) used in seismic studies.
Military - Bases, Military - Historic, Scientific - Test Facility
Links: en.wikipedia.org
By: robsv