Those are fabulous photos, but they clearly show why the airport's days are numbered.
The reason for the field (well, not originally, but fairly early on) was the Douglas plant. Since that merged with McDonnell and moved to Long Beach, the airport lost its reason for existing. Few airports can survive indefinitely in an urban environment unless they have scheduled airline traffic or a factory, or there is some reason why the land is unsuitable for other development. The land is just too valuable otherwise.
The Northrup field is still there, but the Hughes one is gone. Same deal. The Lockheed field survived by going commercial in a big way (it's KBUR).
It's amazing how many of the LA area airports are there because of aircraft manufacturers. McDonnell Douglas is in Long Beach for the moment (not much longer), Robinson is at Torrance, every defense contractor in existence is at Palmdale, etc.