Mogami clan
During the Sengoku period, the area was under the control of the Mogami clan who built Oguni Castle. During the Edo period, parts of the area came under the control of Shinjō Domain. After the start of the Meiji period, the area became part of Mogami District, Yamagata Prefecture. The villages of Higashi-Oguni and Nishi-Oguni were established on April 1, 1889 with the creation of the modern municipalities system. These villages merged to form the town of Mogami on September 1, 1954.