USS Glacier (AGB-4) (later USCGC Glacier (WAG/WAGB-4)) was a U.S. Navy, then U.S. Coast Guard icebreaker which served in the first through fifteenth Operation Deep Freeze expeditions. Glacier was the first icebreaker to make her way through the frozen Bellingshausen Sea, and most of the topography in the area is named for her crew members. When built, Glacier had the largest capacity single armature DC motors ever installed on a ship. Glacier was capable of breaking ice up to 20 feet (6.1 m) thick, and of continuous breaking of 4-foot (1.2 m) thick ice at 3 knots (5.6 km/h; 3.5 mph).