As early as the beginning of the sixteenth century the route by sea to the mouth of the River Ob was well known to Russian traders; though in those days they avoided the passage round the Yamal Peninsula by dragging their small vessels over the rivers and lakes of the Peninsula, as far as Ob Bay. In the first half of the seventeenth century, however, trading navigation to Ob Bay was brought to a standstill by an interdict placed on it, in 1619, by an Ukase of the Muscovite Government.