There have been rumors for a long time that "Wright-Pat" is the real "Area 51", but I have to say that I'm more convinced by @Ephraimite's remarks about Truth or Consequences, New Mexico being the real "Area 51" due to Phil Schneider's convincing remarks... But that's not to say that there's not things going on in BOTH or in many more locations.
At this point I'm convinced that the entire USA is just about entirely blanketed with "DUMBs" or Cavern Worlder zones for both interaction, manipulation points, entry/exits, etc. etc. etc. etc. (Especially after seeing USA's Camp David's Cavern World Connection .)