Formally, Lake Superior, Lake Michigan, Lake Huron, Lake Erie and Lake Ontario. Geologically, there are only four lakes — Huron and Michigan are actually two wings of the same lake (they have the same water level). For an argument in favour of six lakes, see Lake Champlain.

The Great Lakes system is a major watershed in North America and includes the previously mentioned 'big five' lakes (Superior, Michigan, Huron, Erie, and Ontario) as well as the lakes rivers and straits which connect them, and the lakes and rivers which flow into and out of them.

The connecting bodies of water are as follows:

The St. Marie's River, which connects Superior to Huron and features the Soo Locks
The Straits of Mackinac, which separate Michigan from Huron
The Huron River, which connects Lake Huron to Lake St. Clair
Lake St. Clair
The Detroit River, which connects Lake St. Clair to Lake Erie
The Niagara River, which separates Lake Erie from Lake Ontario, featuring Niagara Falls
The Welland Canal, which by-passes Niagara falls
The St. Lawrence River, which flows from Lake Ontario to the sea.

Some of the major tributaries of the Great Lakes System are:

Lake of the Woods in Northern Minnesota and Ontario, and the Rainy River through which it flows to Superior
Lake Nipigon, in Northern Ontario and the Nipigon River through which it flows to Superior
Lake Nipissing, in Northern Ontario
Lake Winnebago, in Wisconsin
The Wabash River in Indiana and Illinois
The Chicago River
The Rouge River system in Michigan
The Thames River in Southern Ontario
The Genessee River in Upstate New York
The Finger Lakes in Upstate New York
Lake Champlain in Vermont
The Ottawa River in Quebec and Ontario

A majority of the population of Canada is concentrated around the Great Lakes System, as is the large industrial swath of the United States known as the Rust Belt with its large population centers.

"Lake Huron rolls, Superior sings
In the ruins of her ice water mansion
Old Michigan steams like a young man's dreams,
The islands and bays are for sportsmen.

"And farther below Lake Ontario
Takes in what Lake Erie can send her
And the iron boats go as the mariners all know
With the gales of November remembered."—Gordon Lightfoot, the Wreck of the Edmund Fitzgerald

Five gigantic inland seas—some of them hundreds of miles wide and as much as a quarter of a mile deep—stretch in a rough line east and west across the Canadian-U.S. border. These lakes have been a key feature of the region, influencing much of the development of this area throughout history.

First, a Little Geology
Five hundred million years ago, the North American crustal plates pulled apart in several directions, forming the North American Rift. The crust broke in some places and subducted in others, making a very wide basin which connected to the ocean, creating a vast, shallow sea. Over the years this depression turned into a huge branching network of river valleys which were crushed down and expanded by repeated visits from big sheets of ice, some as much as two kilometers thick.

Twelve thousand years ago, the ice withdrew again, enlarging and defining the existing hollows in the North American landscape. Soft rock, such as sandstone, was scooped out, while harder dolomites resisted, producing distinctive shapes for the coastlines. The big lakes filled with fresh water from the melting glaciers and overflowed into myriad streams, rivers, and fecund young wetlands.

The lakes thus formed were vast, scattered all over North America. Only the familiar five have survived to modern times. Among the ones which did not make it:

  • Lake Bonneville once covered most of what is now Utah, but it dried up, leaving only a vestige which we call the Great Salt Lake.
  • Lake Shoshone, which once covered southern Idaho, drained out down the Snake River.
  • Lake Agassiz (named for eminent Swiss geologist Louis Agassiz, whose theoretical work helped form the basis for our understanding of glaciation) covered a huge swath of Ontario, Minnesota, and North Dakota. It eventually silted in, leaving many smaller, shallower lakes.
  • Lake Missoula described a torturous, twisty path through the Montana Rockies—at some points it was only a few miles across. Its waters sat behind an enormous glacial remnant which melted and shattered under the water pressure. The resultant deluge scoured the plains of eastern Washington bare to the bedrock.

Other glacial lakes drained into one another, overflowed, and merged. Eventually the Great Lakes became the five that are familiar to us today.

The lakes became vital habitats for countless species of plants and animals; also important to the humans of the area. These vast lakes contain about a fifth of the fresh water in the world, gained by precipitation, streams, and runoff. They feed some of the most important waterways in the region, principally St. Lawrence River and the Chicago River.

And, a Dash of History
The lakes are big—upon crossing Lake Michigan, French explorer Jean Nicholet assumed he had crossed the Pacific Ocean. He donned silk robes which he imagined would be appropriate for meeting the dignitaries of China. I'm sure the Native Americans of the region thought he was eccentric enough even without the getup. Explorer Samuel Champlain called the gigantic lakes sweet seas (mers douces).

The lakes connect and service such ports as Chicago, Cleveland, Detroit, and Toronto. Some of the Great Lakes' ports are as much as 1,000 miles (1,600 km) inland. Several elaborate sets of canals and locks connect the whole show together: the St. Lawrence Seaway, the Soo Locks (on St. Mary's River), the New York State Canal System, and the Chicago Sanitary and Ship Canal, which allows shipping to the Illinois River, the Mississippi River, and down to the the Gulf of Mexico.

One of the most extensive and important inland waterways in the world, the Great Lakes and their attendant connections have greatly facilitated industrial development in North America, playing a crucial role in the economic success of key industries such as steel and agriculture.

Since the mid-19th century the lakes have had quite a lot of problems with pollution, particularly industrial waste and sewage. Meanwhile, irrigation projects in the midwest caused the water levels to fall, and development projects which filled in the wetlands also threatened the five lakes. The pollution became so famously horrible that Lake Erie was a popular punchline for late-night talk show monologues and satirical magazines by the mid 1970s. Since that time, the state, provencial, and local governments have made a huge cleanup effort. As of this writing, the Great Lakes have rebounded, and are once again a haven for fish and wildlife, and clean water for human use. Some lingering toxic effects remain, but the future looks surprisingly bright for the lakes.

Finally, a bit of Geography

  • Lake Superior: is the largest of the lakes, with a surface area of 31,700 square miles (82,100 square km) and nearly 3,000 miles of shoreline (4,400 km). It is the largest freshwater lake (by surface area) in the world.
  • Lake Huron: second only to Superior in size, this lake is 23,000 square miles (59,570 sq. km). Third biggest by volume (it is relatively shallow, under 200 feet on average. Connected to Lake Michigan by the Straits of Mackinac.
  • Lake Michigan: in the middle, size-wise, it is bigger than Erie and smaller than Huron, although it is second largest by volume. It is the only one of the five which is entirely within the borders of the United States.
  • Lake Erie: is next-to-smallest. It is fairly shallow (average 62 feet) and by volume it is the smallest lake, which is a large part of the reason that pollution was such a problem for this lake.
  • Lake Ontario: smallest of the Great Lakes, it is only 7,320 square miles (almost 19,000 sq. km.), although it has a greater average depth (and consequently a greater volume) than Lake Erie.

The lakes have been the bane of many geography students in the United States (and I assume our northern neighbours don't have an easier time with it). So, I present here an easy mnemonic to remember the five Great Lakes' geographic relationship to one another:

Only Elephants Have Massive Snouts

From easternmost to westernmost, like so:


If you prefer going the other direction (westernmost to easternmost), you could use:

Some May Have Eggs Only

CST Approved

reworked and revised: June, 2007
E2 Nodes on each lake by hamster bong
Special thanks to Joel D, my Canadian pal, for a little bit of info that made it even better
Ashworth, William, "The Late, Great Lakes" (Knopf, New York, 1986).
The World Book Encyclopedia (I know, I know!), 2001 edition, articles about the specific lakes and the Great Lakes article.
Benne, Bart, "Waspleg and Other Mnemonics" (Taylor, Dallas, 1988) (for the Elephant one, the other one is my own concoction)

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