There are many theories as to how the regional name of Niigata came about, but no accurate records are said to remain. Facing the Sea of Japan, the whole of Niigata prefecture receives heavy snows in winter, particularly the mountainous areas. Since ancient times, the seaside districts developed as important marine transport hubs and by 1700, Niigata-cho (Niigata town) became the largest port town on the Sea of Japan coast. Meanwhile, Sado was known from ancient times as an island that yielded gold, and was heavily developed in the Edo period (1603-1868) as a territory under direct control of the Edo government. As Sado's forests were carefully preserved to secure wood for use in the gold mine, the island was also the last habitat of the Japanese crested ibis.