Until after the Meiji Restoration, the area that is now Niigata Prefecture was divided into Echigo Province (on the mainland) and Sado Province. During the Sengoku period, the Nagao clan, who were at times vassals to the Uesugi, ruled a fief in the western part of modern Niigata from Kasugayama Castle. The most notable member of the Nagao clan was Nagao Kagetora, later and better known as Uesugi Kenshin. He unified the leaders of Echigo Province and became its sole ruler. By taking the surname Uesugi, he also became the head of the Uesugi clan and effectively brought their realm under his control.