Mining began at Nakaosaka Iron Mine, just north of Shimonita, in the 1840s, making it one of Japan’s earliest iron ore mines. High-grade magnetite iron ore was found in Nakaosaka in sufficient quantities to make the mining effort worthwhile, even in early times before the introduction of modern iron smelting.
After the Meiji Restoration of 1868, the mine was briefly taken over by the government, and one of the three most significant iron works in industrializing Japan was built there. Later, the mine was privatized. With the help of Western advisors and ready access to essential components such as coal and lime, Western-style blast furnaces made Nakaosaka the most modern steel mill in Japan by the turn of the century. The steel works reached its peak in the World War I years. The refinery closed after that, with limited mining continuing until 1961.
The site is now a ruin. From the gate, visitors can see the tracks where minecarts once ran, as well as remnants of the blast furnaces.