Show international boundary markings the land part of the international boundary between the united states and canada which is about 1749 miles in length is marked variously with monuments of iron aluminum bronze set on concrete stone calms cairns and concrete placed at points ranging from two and a half to four miles apart A vista has been cut through the trees where the line runs over wooded areas the water part of the boundary is defined by courses and distances between turning points that are referred to as lighthouses or markers ol of metal or concrete on the shores of lakes and banks of streams |