A Historical Geography of the Regional Centres in the Ancient Tohoku Frontier District
About the middle of the 7th century the Tohoku district attracted attention of ancient states under the System of Ritsuryo for their northern frontiers. Shiro or Saku (ancient castle) of both Mutsu and Dewa Kunis (ancient prefectures) were administrative centres as well as frontier forts in the northern borderland. In addition to these were there stationed Gundan, a purely military position and Gunke (Kohri-no-Miyake), an administrative centre of Kohri (ancient county), substructure to Kuni. It is supposed that to these regional establishments are practised gridded urban planning similar to those of Teito (ancient megalopolis) and Kokufu (ancient local capitals).The authors did researches on the urban planning of the ancient regional centres by following the methods of historical geography, comparing with their micro-topography and the present landscapes, examining Koaza (the smallest place name) on the land register maps. The objectives examined were Akita Jyo, Tamatsukuri Gundan, Mutsu-no-Kuni Shimeha-Gunke, Dewa-no-Kuni Murayama-Gunke, and so forth. The results show that there were the gridded plans as in Taga Jyo, Izawa Jyo, and Kinowa-no-Sake, reported already.Secondly, the authors investigated in what location those regional centres were situated in the view point of ancient topography and communication. Especially in respect to the way connecting Taga Jyo with Akita Jyo, we considered its probable route, by making field survey near the Sarubane Toge (pass), and examining its topographical position and attempting to identify the Sarubane Eki (stage).At the same time we investigated the Gridded Pattern, the land so-called Jori form practised under the System of Ritsuryo, near and around these regional centres mentioned above, its forms, areas and limit of distribution. Consequently, we can report such newly found areas with remains of the gridded land pattern as in the valleys of Naruse and Hazama rivers, and observe that allotted lands in each Tsubo, in general, adopt a peculiar form. As to the northern limit of its distribution the line is supposed to be drawn from Morioka to the Akita plain.To the north of the area distributing ancient castle and the gridded land pattern, there was located Noshiro-no-Tamuro, the northernmost fort of the Ritsuryo states. It is considered to be located on the plateau to the south of the Yoneshiro river.