one of the finest natural harbours of Western Australia's south coast. An inlet of the Indian Ocean, the sound, with a surface area of 35 square miles (91 square km), has an entrance 5 miles (8 km) wide flanked by Bald Head on the southwest and Cape Vancouver on the northeast. Its shores are generally steep and rocky. Breaksea and Michaelmas islands lie within the sound, which has two extensions, Oyster Harbour (north) and Princess Royal Harbour (west), the site of the port for the city of Albany. The inlet, charted (1791) by Captain George Vancouver and named by him after the reigning English king, was used as a whaling base as early as 1801. The King George III Sound settlement, predecessor of Albany, was founded in 1826. During World War II, the inlet was used as a U.S. naval base.