The area of present-day Hachimantai was part of ancient
Mutsu Province. The area was dominated by the
Nanbu clan from the early
Muromachi period. During the
Edo period Tokugawa shogunate, the area was under
Morioka Domain, and was divided between
Ninohe District in the north and
Iwate District in the south. In the early
Meiji period, the village of Arasawa was created within Ninohe District on April 1, 1889, with the establishment of the modern municipalities system. Arasawa merged with neighboring Tayama Village on September 30, 1956, to form the town of
Ashiro. Ashiro was transferred to Iwate District on April 1, 2002. Likewise, on April 1, 1889, the villages of Tairadate, Obun, Dendo and Terada were established within Kita-Iwate District. Kita-Iwate was merged with Minami-Iwate in 1896. The four villages merged on September 30, 1956, to form the town of
Nishine. The city of Hachimantai was established on September 1, 2005, from the merger of the towns of Ashiro and Nishine, and the village of
Matsuo. ==Government==