One of the three great ports, it thrived as a commercial harbor with Echigo Fuchu and the Shinano region as its hinterland. Uesugi Kenshin protected it as a financial base; after the Uesugi clan's transfer, it served as an outer harbor under the castle-town policies of the Hori and Matsudaira clans.
Medieval names included Imamachi harbor and Naoe-no-tsu; since the Seki River mouth also shifted, the coordinate represents the river mouth area near old Imamachi.
Certainty: HighHow far the account above is supported by the cited sources. It does not refer to the precision of the coordinates or the dating.
See it on the 1467 map