In 1785 Japanese explorers almost reached the Strait of Tartary to the west, Cape Patience to the east and Urup in the Kurils. In 1808 Mamiya sailed up the east coast and Matsuda Denjuro up the west coast. From near Cape Patience, Mamiya crossed the mountains to join Matsuda. The next year Mamiya sailed into the mouth of the Amur River and reached a Chinese trading post. In 1852 Mamiya's maps were published in Europe by Philipp Franz von Siebold.
