The Great Lakes region of Northern America is a binational Canadian–American region centered around the Great Lakes that includes the U.S. states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin and the Canadian province of Ontario. Canada's Quebec province is at times included as part of the region because the St. Lawrence River watershed is part of the continuous hydrologic system. The region forms a distinctive historical, economic, and cultural identity. A portion of the region also encompasses the Great Lakes megalopolis.
State and provincial governments are represented in the Conference of Great Lakes and St. Lawrence Governors and Premiers, which also serves as the Secretariat to the Great Lakes St. Lawrence Compact and the Great Lakes–Saint Lawrence River Basin Sustainable Water Resources Agreement.
The Great Lakes region takes its name from the corresponding geological formation of the Great Lakes Basin, a narrow watershed encompassing the Great Lakes, bounded by watersheds to the region's north by the Hudson Bay, to the west by the Mississippi, and to the east and south by the Ohio. To the east, the rivers of St. Lawrence, Richelieu, Hudson, Mohawk and Susquehanna form an arc of watersheds east to the Atlantic.
The Great Lakes region, as distinct from the Great Lakes Basin, defines a unit of sub-national political entities defined by the U.S. states and the Canadian province of Ontario encompassing the Great Lakes watershed, and the states and province bordering one or more of the Great Lakes.
Geography
The Palaeozoic strata are parts of a great area of similar layers hundreds of feet in thickness. These strata decline gently southward from the great upland of the Laurentian Highlands of eastern Canada. The visible upland area of today was a small part of the primeval continent with the remainder of it still buried under a Palaeozoic cover. The visible part was the last part of the primeval continent to sink under the advancing Palaeozoic seas. This district may be considered an ancient coastal plain. The weaker layers are worn down in sub-parallel belts of lower land between the upland and the belts of more resistant strata, which rise in uplands. Illustrations of this type of forms are found in the district of the Great Lakes. The chief upland belt or escarpment is formed by the firm Niagara limestone/dolomite, which takes its name from the gorge and falls cut through the upland by the Niagara River. The Niagara Escarpment has a relatively strong slope or enfacing escarpment on the side towards the upland, and a long gentle slope on the other side. Its relief is seldom more than 200 or and is generally small. Its continuity and its contrast with the associated lowlands on the underlying and overlying weak strata make it an important feature. The escarpment would lie straight east–west if the slant of the strata were uniformly to the south. However, the strata are somewhat warped and so the escarpment's course is strongly convex to the north in the middle, gently convex to the south at either end.
The escarpment begins where its determining limestone/dolomite begins, in west-central New York. There, it separates the lowlands that separate Lake Ontario from Lake Erie. It curves to the northwest through the Ontario province to the island belt that divides the Georgian Bay from Lake Huron. From there, it heads westward through the land-arm between Lake Superior and Lake Michigan and southwestward into the narrow points dividing Green Bay from Lake Michigan. Finally, it fades away with the thinning out of the limestone and is hardly traceable across the Mississippi River. The arrangement of the Great Lakes closely matches the course of the lowlands worn on the two belts of weaker strata on either side of the Niagara escarpment. Lake Ontario, Georgian Bay and Green Bay occupy depressions in the lowland on the inner side of the escarpment. Lake Erie, Lake Huron and Lake Michigan lie in depressions in the lowland on the outer side. When the two lowlands are traced eastward, they become confluent after the Niagara limestone has faded away in central New York, and the single lowland is continued under the name of the Mohawk Valley. This is an east–west longitudinal depression that has been eroded on a belt of relatively weak strata between the resistant crystalline rocks of the Adirondacks on the north and the northern escarpment of the Appalachian plateau (Catskills-Helderbergs) on the south. Early in U.S. history, this provided a vital economic route between the Atlantic seaports and the U.S. interior.