In 1914, during the period of Japanese colonial rule, Jeongui prefecture and Daejeong prefecture were merged into Jeju-gun ("gun" meaning an administrative district bigger than a prefecture), and the two centers of Seogwipo became Jeongui-myeon and Daejeong. In 1915 the names were changed a second time, to U township and Jwa township. In 1935 the two townships were given the names they still have today: Seogwi and Jungmun. Seogwipo was greatly affected by Japanese colonial rule - it was used as a base that supplied marine products, and a whale processing plant was built near the port of Seogwipo. Twelve artificial caves made by the Japanese army still remain along the coast near Sammaebong Peak.