Read here at Gizmodo, h/t Hot Air.
Seven examples given from Google searches.
Suggestions include weapon targeting grids, calibration lines for space observations and a general sense of puzzlement.
A second site looks like the picture below but with a boundary line.
Second photo has an 18 mile long grid pattern just to the left of the green marker and at about a sixty degree angle. Link to Google.
The Google zoom links for the others are at the Gizmodo site.
This answer seems definitive, that it serves spy satellite technology as other structures once helped the US.