I'm pretty sure it's Key West, Florida.
That's also the only major city in the continental U.S. in which the temperature has not dropped below freezing during the past 30 or 40 years. The last time I checked, the lowest temperature was 43° F.
Santiago, Chile
That depends on what you term a "major city" . I would say that Bahia Blanca, a city of 300,000 fits that description, but others may differ.
The European capital that is farthest south is Valletta, the capital of Malta.
The capital that is farthest south is Kampala
Ozette, Washington is the westernmost city in the continental US.
dover
capetown
Xoconocho
Narita Airport (60 KM) from the city to the airport in Japan.
Ushuaia, Argentina is the southernmost city in world
Corpus Christi, TX
Columbia