McMurdo

The American Base at McMurdo is sometimes on the itinerary of cruise ships, it is far and away the largest Antarctic base with a summer population (when the tourist ships can get in) of around 1000 falling to  250 in the winter.

The next largest base has a summer compliment of 250 with several more in the 100's. 80%+ of bases have a summer compliment of less than 100 people, the winter crew is usually between about a half and a quarter of the summer compliment.

Antarctic Bases - Seasonal Populations