From the Great Lakes to the Atlantic ocean......................via Canada...................the US - Canadian border...............the longest unguarded border in the world.........

Map[edit]

Map of the North American Great Lakes and the Saint Lawrence Seaway from 1959, depicting the entire length beginning at the Gulf of Saint Lawrence in the east to the western-most terminus at Lake Superior. This map is in the public domain and is available at Wikimedia Commons in several resolutions.