Although the silver mines in Iwami were exploited from the 16th century, the history of the daikansho starts under the Tokugawa Shogunate. In 1601 Ôkubo Nagayasu was appointed as overseer (termed Bugyō) of the mines and Ômori-daikansho was built as his offices. It appears there were more fortifications closer to the mines and on the surrounding mountains besides, including at least four castles, such as Yamabuki Castle, to add to the area's defences, although the daikansho's role was chiefly administrative. Ômori-daikansho was also known as Mukai-jin'ya. Early overseers were officially titled Bugyō, and the term Daikan was used thereafter and throughout most of the Edo Period, but there were other official terms employed besides. Ôkubo had an income of 20,000 koku, basically encompassing the whole province, but subsequent rulers were more humbly enfeoffed (overseer Takemura, who came after Ôkubo, earned only 1,000 koku), and the general trend was that the role became a much less lucrative position over time. In 1902 the main hall of the daikansho was re-built as the Nima District Hall, but the surrounding walls and nagayamon gatehouse were retained from the Edo Period. The silver mines continued to operate until 1923. In 2007 the daikansho was part of over a dozen sites inscribed as part of the Iwami Ginzan World Heritage Site.
The famous Iwami Ginzan (Iwami Silver Mines), a World Heritage site since 2007, were of great economic significance to the Shogunate and thus fell under its direct control. But actual administration fell upon the Daikan (Shogunal Representative) who ran things from here. The site consists of original structures: the nagayamon (row house and gate house combined), built in 1815. The main hall, which now serves as the Iwami Ginzan Museum, was built in 1902 as the Nima District Hall. The latter's architecture, though evidently Meiji Period, is the inheritor to a form typical to daikansho (as seen at the Mizuhara-daikansho, for example), but I don't know how similar it is to the original main structure. I'm sharing this also to contextualise the Kawashima-bukeyashiki (samurai residence), also found in Ômori.
The museum features exhibitions on rice, old face masks (Fukumen), silver mines, a map of silver mines in Japan, a map of daikansho and jin'ya in the Edo Period, and information about the daikansho, such as a complete list of office-holders and schematics of the site's floor plan.
|English Name||Ohmori Daikansho|
|Castle Condition||No main keep but other buildings|
|Designations||UNESCO World Heritage Site, National Historic Site|
|Historical Period||Edo Period|
|Artifacts||Nagayamon, Castle Town, Bukeyashiki|
|Features||gates, samurai homes, walls, castle town|
|Access||Nima Station; nine minutes by car / taxi|
|Visitor Information||9:00-17:00; 550yen for Japanese, 450yen for foreign visitors|
|Time Required||60 minutes|
|Location||Oda, Shimane Prefecture|
|Coordinates||35° 7' 18.98" N, 132° 26' 52.91" E|
|Added to Jcastle||2020|
|Admin Year Visited||Viewer Contributed|