Ulleung Island, volcanic island, North Gyeongsang do (province), South Korea. Ulleung Island is the main island of Ulleung county, South Korea’s least populated county, and is surrounded by 44 smaller rocky islands, most of which are without permanent habitation and some of which are claimed by Japan. It lies in the East Sea (Sea of Japan), 75 miles (120 km) off the northeastern coast of South Korea, and has an area of 28 square miles (73 square km). Before its domination by the Silla kingdom (57 bce–935 ce) in 512, it was an independent kingdom named Usan-guk. The island’s summit, Seongin Peak (3,228 feet [984 meters]), has a caldera crater.
Ulleung Island is divided into three administrative regions: the town of Ulleung-eup and the rural townships of Buk-myeon and Seo-myeon. The entire coastline has rocky bluffs 100–300 feet (30–90 meters) high, which preclude port development. Neighboring waters with the interchange of warm and cold currents offer good fishing ground for cuttlefish, which is exported, and various other marine products. Agricultural products, however, must be imported. The mountain area produces Chinese juniper, birch, and princess trees, all used to make quality furniture. Ulleung Island is connected with the mainland by regular sea routes. Pop. (2020) 8,444.