Canada - Showing The Narrows St. John's - Showing The Narrows St. John's. The Narrows, the only entrance to St. John's Harbour, Newfoundland, is a narrow channel between the Southside and Signal hills. It has a least depth of 11 metres and at its narrowest point near Chain Rock is 61 metres wide. The Narrows has served an important defence of the city of St. John?s from early pirates and settlers in 1655 to World War II.. Part of Box 160 Modern New York, Boswell collection.