Sanshin-shichiso is a general term for port cities of Sanshin and Shichiso defined as Japan's ten most important ports and harbors in "Kaisen Shikimoku," --the Oldest Sea Law of Japan established in the late Muromachi period.
Sanshin consists of three ports: Anotsu in Ise Province (Tsu City), Hakatanotsu in Chikuzen Province (Fukuoka City), and Sakaitsu in Izumi Province (Sakai City).
Shichiso consists of seven ports: Mikuniminato in Echizen Province (Sakai City), Wajimaminato in Noto Province (Wajima City), Iwaseminato in Ecchu Province, (Toyama City), Imamachiminato in Echigo Province (Naoetsu) (Joetsu City), Tsuchizakiminato in Dewa Province (Akitaminato) (Akita City), and Tosaminato in Tsugaru region (Goshogawara City).
During the Medieval Period, these Sanshin-shichiso flourished through trading with the Korean Peninsula and the Chinese continent when the Japan Sea Trade was active. In the early-modern times, they flourished as ports of call of Kitamae-bune, cargo vessels, but most ports on the Sea of Japan side began to decline after the Meiji restoration.
"The Bubishi" (Records of Military Preparation), a historical book written in the Chinese Ming Dynasty named Hakatanotsu, Anotsu, and of Bonotsu in Satsuma Province as Japan's Sanshin.