Until the opening of the Seikan Tunnel in 1988, ferries were the main means of transport between Honshu and Hokkaido, and Aomori served as a hub for ferry-to-ferry transfers. With the opening of the railway tunnel, the ferries lost much of their importance, although car ferries still connect Aomori with Hakodate today. One of the former ferries, the Hakkodamaru (八甲 田 丸, Hakkōdamaru), today serves as a memorial to the bygone era.
After their last journey in 1988, the Hakkodamaru retreated to the port of Aomori, where it remains permanently moored as a museum ship. Two of their sister ships, the Masumaru and the Yoteimaru, have also been converted into museum ships and can be seen in the port of Hakodate or in the Maritime Museum in Odaiba.