Russian "Pomors", the coastal dwellers of the White Sea shores, explored this sea and the coast of Novaya Zemlya since the 11th century. The Arctic's first shipping line, the Great Mangazea Route, from the White Sea to the Ob River and the Yenisei Gulf began operating in the latter part of the 16th century. This line opened up the way to Siberia's riches and it worked until 1619, when it was closed for military and political reasons, for fear of possible penetration by Europeans into Siberia.