Tosaminato Site

Tosaminato Site: A Medieval Port Town on a Sandbar

The Tosaminato Site (十三湊遺跡, Tosaminato Iseki) is the site of a medieval port town that flourished from the early 13th to the late 15th century at Jusan, Goshogawara City, Aomori Prefecture, designated a national Historic Site in 2005.

According to the Agency for Cultural Affairs, the site lies on the west shore of Lake Jusan, a lagoon at the mouth of the Iwaki River midway along the Sea of Japan side of the Tsugaru Peninsula. The Kaisen Shikimoku, a maritime code thought to date from the Warring States period, names Oshu Tsugaru Tosaminato among the "three ports and seven harbours" of Japan, showing its importance in medieval northern Japan.

Aomori Prefecture notes additions to the designated area in 2006 and 2007. The site is owned by Goshogawara City and others.

Why It Was Designated

Tosaminato was said to have prospered as the base of the Ando, a powerful Tsugaru family who governed relations with the north, but tradition held that a tsunami destroyed it in the fourteenth century, and it long remained a "phantom port". Systematic excavation from fiscal 1991 by the National Museum of Japanese History, Shiura Village and the Aomori Prefectural Board of Education revealed the extent of the town.

The site occupies the tip of a sandbar between the Maegata channel and Lake Jusan, about 2 kilometres north to south and up to 500 metres wide. A great earthwork with a dry moat divides the core east to west; the northern part is thought to have housed the lord and his people. From the later 14th century, fenced east-west streets were laid out at intervals of 20 to 30 metres, with post-built buildings, wells and smithing and copper-working workshops between them, a planned urban layout. A major fire struck in the early 15th century, possibly linked to the Ando defeat by the Nanbu in 1432.

Townhouses are thought to have stood south of the earthwork, and about 300 metres further south the Danrinji temple site holds two square enclosures, each over a hundred metres a side. By the Maegata channel, bank-protection posts and planks and posts wrapped with rope, possibly from a jetty, were found. The Agency calls the Tosaminato Site a rare example of a large site with an important harbour, well preserved because most of it was never redeveloped, set in fine lake and coastal scenery.

What to Look For

No buildings stand above ground. What matters is the setting: a long, narrow sandbar between the Sea of Japan and the lake, where harbour, town and lord's residence once stood side by side. Walk it with that picture in mind.

Finds and detailed explanations are at the Shiura History and Folk Museum. Goshogawara City says it displays fine ceramics, iron and bronze objects and glass beads from the north, alongside the history of the Ando and related sites such as Fukushima Castle and the Sannobo temple site.

Visiting the Tosaminato Site

The Tosaminato Site is an outdoor site, listed by Aomori Prefecture as open to the public; no fee is mentioned.

According to Goshogawara City, the Shiura History and Folk Museum (Jusan Tosa, Goshogawara; 0173-62-2775) opens from 9 a.m. to 4 p.m. and closes from 1 December to 31 March. Admission is 310 yen for adults, 220 yen for university students and free for high school students and younger.