This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Four of the five Great Lakes, Superior, Huron, Erie and Ontario, straddle the international border between the United States and Canada, and the fifth, Lake Michigan, lies entirely within the United States but drains into the same connected system, so the lakes function as one shared hydrological and economic system regardless of the line drawn through the middle of four of them. That shared geography built one of the busiest inland shipping corridors on Earth: the St. Lawrence Seaway, completed in 1959 through a joint US-Canadian engineering project, opened a navigable route from the lakes all the way to the Atlantic, letting ocean-going vessels reach ports as far inland as Duluth, Minnesota, over two thousand kilometers from the sea. Cities on both shores, Chicago, Detroit, Cleveland and Toronto among them, grew into industrial centers precisely because the lakes gave them cheap water transport to move raw materials and finished goods in every direction at once. Governing a shared resource that size across an international border has needed its own machinery too, formalized in the 1909 Boundary Waters Treaty and the joint bodies it created, among the oldest continuously operating instances of two countries managing one body of water together.