McMurdo Station is an American Antarctic research station on the southern tip of Ross Island. It is operated by the United States through the United States Antarctic Program (USAP), a branch of the National Science Foundation (NSF). The station is the largest community in Antarctica, capable of supporting up to 1,200 residents, though the population fluctuates seasonally; during the antarctic night, there are fewer than two hundred people. It serves as one of three year-round United States Antarctic science facilities. Personnel and cargo going to or coming from Amundsen–Scott South Pole Station usually first pass through McMurdo, either by flight or by the McMurdo to South Pole Traverse; it is a hub for activities and science projects in Antarctica. McMurdo, Amundsen-Scott, and Palmer are the three non-seasonal United States stations on the continent, though by the Antarctic Treaty System the bases are not a legal claim (though the right is not forfeited); they are dedicated to scientific research. New Zealand's Scott Base is nearby on Hut Point Peninsula, as is Arrival Heights Laboratory. On the base is a heliport, and across the channel is a helicopter refueling station at Marble Point, but the main airfields in the 2020s are Phoenix Airfield and Williams Field which are to the south and built on ice. Winter Quarters Bay is the base seaport, though access can be limited by weather conditions when the sea ice forms. Weather can make it too hard to land aircraft, and an icebreaker may be needed to reach the port facility. However, the sea ice also makes it possible to make ice traverses and travel directly across the bay, and historically an Ice Runway was crafted. The base is powered by a mixture of generators and wind power, though it had a nuclear reactor in the 1960s.
The base was first established in the mid-1950s as part of an international program to study and explore Antarctica for peaceful purposes. Daylight is seasonal at McMurdo, corresponding to the south polar daytime, and the polar night, which is also winter, lasts from about April to September. As it warms, the sea ice melts, and the port is opened, but by about February, much of the activity drops with plunging temperatures and increasing darkness, and there are usually no flights in or out until July or August.