The historic district of Onyu is located at the intersection of the Wakasa Kaido road and the Harihatagoe Pass (or Negorizaka Slope), two major roads of the Saba Kaido (“Mackerel Road”), a network of trade routes that connected Obama with the ancient capital of Kyoto. Onyu was an important location in the former Wakasa Province, containing the ichinomiya (the highest-ranked shrine of the region; now Wakasahiko Jinja and Wakasahime Jinja Shrines), Kokubunji Temple, and the provincial government office. Wakasa Province was a miketsukuni, an area tasked with sending food and salt to the imperial court. Before the post town of Kumagawa-juku was established in the mid-sixteenth century, the market in front of Wakasahime Jinja Shrine served as the base of shipping operations, facilitating the transport of various goods along the Saba Kaido.
In the Edo period (1603–1867), Onyu businesses prospered by processing agate brought from the north on kitamaebune trade vessels and sending the finished goods to Kyoto and Osaka. To this day, the area retains a traditional atmosphere, and many historic houses can be seen along the streets of Onyu.
