The vehicles in the ground surface lot belonged to construction workers and the FAA Tower cab is not finished yet. The Airport Hotel has not been constructed yet in the area where the roof is darker. The office tower for the Port Authority and the FAA radar rooms and offices is complete. I suspect this photo was taken a few months before the grand opening of the terminal later in 1959 because there are no oil stains on the ramp yet from the piston aircraft in use at the time (DC-4's, DC-6's, DC-7's, Lockheed Constellations, etc.).

Note the small short-term parking lot on the second floor in front of the terminal and the covered walkways out into the huge parking lot.