THE ELUSIVE S-4 (Site 4), nowhere to be found south of Area 51 except in this “modified” air chart of unknown origin.
In Nevada, the only recognized Site 4 is in the Electronic Combat Ranges around Tonopah Test Range, Nevada.
In Southern California there is a Site 4 (Northrop Grumman) at the Air Force Plant 42 in Palmdale.
Site 4 (in Palmdale) used to be the most classified facility in Plant 42 when the B-2A was in development and construction.
Presently this Site 4 (in Palmdale) is used by both Lockheed and Boeing for the JSF Program.
The only thing correct about this “modified” art chart is the location of Sandia Labs’ operations location.