If they are not L4 they have to be J3 (I wonder how could we guess with the cockpits all covered in tarpaulins...You would have to see the tarpaulin is too short to cover the extended fuselage plexi of a L4 cockpit?).
Then it has to be related to the CPTP/WTS program, and many were the airfields with CPTP/WTS schools...
Could it be Rhode Island?