Usakumai Ruins

An Open-Air Museum Spanning Seven Millennia

The Usakumai Site Cluster comprises twenty-two distinct archaeological sites distributed along the Usakumai Plateau, a long, narrow tableland flanked by two rivers about five kilometres west of central Chitose. What makes this cluster so significant is the remarkable continuity of habitation it documents. Archaeologists have identified two Early Jōmon sites, two Initial Jōmon sites, four Middle Jōmon sites, two Late Jōmon sites, two Final Jōmon sites, five Epi-Jōmon (Zoku-Jōmon) sites, and eleven Satsumon-period sites within the protected area. Numerous Edo-period charcoal kilns have also been documented, extending the human story almost into modern times.

The reason for this long human presence is no mystery once you stand on the riverbank. The Naibetsu River, though only 2.5 kilometres long, is fed by more than sixty natural springs and ranks among Japan's official "Hundred Famous Waters" (Meisui Hyakusen). Salmon return each autumn to spawn, just as they have for thousands of years. For successive generations of Indigenous peoples, this was a place of abundance, clean water, and reliable food.

Why It Was Designated a National Historic Site

The designation reflects three exceptional values that set Usakumai apart from other Hokkaido archaeological sites. First, the site cluster preserves an unbroken cultural sequence rarely found in such concentration—from the earliest Jōmon hunter-gatherers through to the historical Ainu. Second, individual sites within the cluster have yielded artefacts of national importance. Third, the geological conditions at certain locations have produced unusually well-preserved organic remains, opening windows into prehistoric environments that are normally lost to time.

Of particular note are the discoveries at Usakumai A, where excavators uncovered twenty-eight burial pits containing grave goods including warabite-tō (warabi-fern-shaped iron swords), small iron knives (tōsu), Satsumon pottery, Hokudai-style pottery, and Haji earthenware. These finds provide concrete evidence of active material and cultural exchange between Hokkaido and the ancient Tōhoku region of Honshū during the Satsumon period (roughly the 7th to 13th centuries CE). The presence of Fujusenpō, one of the twelve imperially issued coins of ancient Japan, further attests to long-distance contact with the mainland.

Usakumai C Site Walking Course

Of the twenty-two sites, only Usakumai C has been developed for public viewing, and it is the most visually striking of all. Here, seventy-nine pit-dwelling depressions from the Satsumon period (approximately 1,100 to 1,300 years ago) remain clearly visible as shallow circular hollows on the forest floor. A self-guided walking course threads between them, with small markers indicating individual dwelling sites and an explanation panel at the trailhead. To stand among so many house pits at once is to glimpse the scale of a thriving Satsumon-period village.

Treasures from Usakumai A and J

Although the Usakumai A burial site is not open to general visitors, replicas and original finds from its excavations are displayed at the Chitose City Buried Cultural Properties Center. The remarkable Usakumai J site contains a peat layer formed from fallen leaves and branches, which has preserved Early Jōmon pottery alongside plant and animal remains—an exceptional condition that may yet yield wooden tools and other organic artefacts as research continues. Other notable finds from across the cluster include a male clay figurine (dogū) from the Final Jōmon period and pottery in the Okhotsk cultural style, suggesting cultural connections reaching as far as the northern Sea of Okhotsk coast.

The Meaning of the Name "Usakumai"

The place name itself carries the memory of Indigenous lifeways. "Usakumai" derives from the Ainu phrase o-sat-kuma-nay, meaning roughly "river mouth—to dry—rack—river." It refers to the wooden racks once used to dry salmon caught here in vast numbers each autumn. The Ainu used uray weirs to catch hocchare—post-spawning salmon prized because their reduced fat content made them ideal for drying and long-term storage. The toponym thus preserves an entire seasonal economy in a single word.

Getting There

The site is most easily reached from JR Chitose Station via the Chūō Bus Shikotsuko Line, which also serves New Chitose Airport. Travellers should disembark at either "Usakumai-bashi" (Usakumai Bridge) or "Fukajō-iriguchi" (Hatchery Entrance); both stops are about a fifteen-minute walk from the Usakumai C trailhead. By car, follow Hokkaido Prefectural Road 16 (the Shikotsuko Park Line) about five kilometres from central Chitose toward Lake Shikotsu, turn right just before crossing the Chitose River, follow the cycling path for 1.3 kilometres, and the trailhead lies just across the next bridge.

Important Safety Notice

Brown bear (higuma) sightings have been frequent in the surrounding forest. Visitors should carry a bear bell, avoid hiking alone, check the latest information from Chitose City before arrival, and refrain from entering during dawn, dusk, or low-visibility conditions. Tall summer grasses can also make the trail difficult to follow during peak season.

Nearby Attractions

The Usakumai area sits within easy reach of several outstanding destinations. Lake Shikotsu, one of Japan's clearest caldera lakes, lies just a short drive further upstream and offers swimming, kayaking, and lakeside walks throughout the warmer months. The Sake-no-Sato Fureai Hiroba and the Chitose Salmon Aquarium ("Sake-no-Furusato Chitose Suizokukan") provide a wonderful complement to a visit, allowing travellers to observe the very salmon runs that sustained Usakumai's inhabitants for millennia. The Naibetsu River Spring Park preserves the namesake spring landscape, and the Chitose City Buried Cultural Properties Center, where many Usakumai artefacts are studied and displayed, is also well worth a stop.