Okinawa Islands
In any case, a flood of archaeological discoveries in the 1970s led Okinawan archaeologists to establish archaeological periods of the Okinawa Islands that were distinct from those of Japan (Amami and the Sakishima group also have unique archaeological periods distinct from Japan and one another). In their framework, the "Gusuku period" is an archaeological epoch of the Okinawa Islands, which they consider was characterized by the widespread appearance of gusuku, the widespread use of iron, and farming. It follows the Shell Mound period and precedes the Sanzan period. It is parallel with the late Heian to Muromachi periods of Japan. Also, the beginning of the Gusuku period corresponds to that of the Old Ryukyu period of Okinawan historiography, both beginning in 1187 with the semi-legendary ascension of King Shunten.