's second largest ocean (after the Pacific Ocean
). With an area of 106,400,000 square kilometres, it covered 20 percent of Earth's surface.
Among the cities on the Atlantic coasts of different continents were New York City, Baltimore and London. At least one Starfleet facility on the Atlantic existed, Starfleet Gander in Newfoundland, Canada. (TOS novel: Spock's World)
The South Atlantic Ocean was often the site of many battles, including those fought between the United States of America and the Brazilian Confederation during the early 21st century. (Star Trek: Accord, Star Trek: Shadowstar Station)
The Transatlantic Maglev Tunnel -- between Montauk, Long Island, New York, and Ireland -- was completed in 2045. (Star Trek: Shadowstar)
By the 24th century, the aquatic city of New Martim Vaz (TNG: "The Survivors") had been built , and the Atlantis Project (TNG: "Family") sought to raise a new continent from the ocean floor.