<P> The Great Lakes coast measures approximately 10,500 miles (16,900 km); however, the length of a coastline is impossible to measure exactly and is not a well - defined measure (see Coastline paradox). Of the total 10,500 miles (16,900 km) of shoreline, Canada borders approximately 5,200 miles (8,400 km), while the remaining 5,300 miles (8,500 km) are bordered by the United States . Michigan has the longest shoreline of the United States, bordering roughly 3,288 miles (5,292 km) of shoreline, followed by Wisconsin (820 miles (1,320 km)), New York (473 miles (761 km)), and Ohio (312 miles (502 km)). Traversing the shoreline of all the lakes would cover a distance roughly equivalent to travelling half - way around the world at the equator . </P> <P> It has been estimated that the foundational geology that created the conditions shaping the present day upper Great Lakes was laid from 1.1 to 1.2 billion years ago, when two previously fused tectonic plates split apart and created the Midcontinent Rift, which crossed the Great Lakes Tectonic Zone . A valley was formed providing a basin that eventually became modern day Lake Superior . When a second fault line, the Saint Lawrence rift, formed approximately 570 million years ago, the basis for Lakes Ontario and Erie were created, along with what would become the Saint Lawrence River . </P> <P> The Great Lakes are estimated to have been formed at the end of the last glacial period (the Wisconsin glaciation ended 10,000 to 12,000 years ago), when the Laurentide Ice Sheet receded . The retreat of the ice sheet left behind a large amount of meltwater (see Lake Algonquin and Lake Chicago) that filled up the basins that the glaciers had carved, thus creating the Great Lakes as we know them today . Because of the uneven nature of glacier erosion, some higher hills became Great Lakes islands . The Niagara Escarpment follows the contour of the Great Lakes between New York and Wisconsin . See also Glacial Lake Iroquois and Champlain Sea . </P> <P> Land below the glaciers "rebounded" as it was uncovered . Because the glaciers covered some areas longer than others, this glacial rebound occurred at different rates . </P>

How many major bodies of water does the contiguous united states border