Just as McCain was born in the Canal Zone.
John Sidney McCain was actually born in Colón, Panama, adjacent to but outside the PCZ, in a normal hospital there (Colón Hospital) equipped with an actual maternity ward (which the rudimentary infirmary/clinic in the PCZ at that time lacked).
Special naturalization legislation actually had to be passed a few years after Panama John McCain’s birth to retroactively enable him and all other similarly situated babies to be recognized as U.S. citizens (not Natty Born Cits).