They hold about a fifth of the world’s surface fresh water. They stretch across eight American states and one Canadian province. They behave so much like oceans, with waves, storms, and horizons you cannot see across, that sailors have long called them inland seas. They are the Great Lakes, five connected freshwater giants that shape the geography, economy, and daily life of North America more than almost any other natural feature on the continent.
The five lakes are Superior, Michigan, Huron, Erie, and Ontario. Together they cover about 94,250 square miles, an area larger than several New England states combined, and hold roughly 5,439 cubic miles of water. That is enough water, as the U.S. Environmental Protection Agency notes, to cover the contiguous United States to a depth of several feet. Yet each lake has its own personality, its own depth, its own shoreline, and its own story. Here is what makes each of them remarkable, and why they matter so much.
The Five Lakes at a Glance
The Great Lakes formed as massive glaciers retreated at the end of the last Ice Age, gouging out deep basins that filled with meltwater. Today the lakes are connected in a chain that flows, in general, from west to east: Superior drains into Huron through the St. Marys River, Michigan connects to Huron through the Straits of Mackinac, Huron flows into Erie, and Erie drains into Ontario, which in turn flows into the St. Lawrence River and on to the Atlantic Ocean.
Hydrologists actually consider Michigan and Huron to be a single body of water, since they are joined at the Straits of Mackinac and share the same surface elevation. By convention, though, we count five lakes, and the differences between them are dramatic. Superior is the giant: the largest by surface area and volume, the deepest, and the coldest. Erie, at the other end of the scale, is the shallowest and smallest by volume, and its water turns over far faster than any of the others.
The U.S. Environmental Protection Agency’s physical data for the lakes tells the story in numbers. Superior covers about 31,700 square miles with an average depth of 483 feet and a maximum depth of about 1,330 feet. Michigan covers about 22,300 square miles, Huron about 23,000, Erie about 9,910, and Ontario about 7,340. Their average depths range from just 62 feet for Erie to 483 feet for Superior, and their volumes range from about 116 cubic miles for Erie to about 2,900 cubic miles for Superior, which alone holds more water than the other four lakes combined. You can explore the full comparison in the EPA’s Great Lakes data.
Lake Superior: The Giant
Lake Superior is the largest of the five lakes by both surface area and volume, and it is the deepest and coldest of the group. Its maximum depth reaches about 1,330 feet, and its water is famously chilly year-round. Superior alone contains roughly half of all the water in the Great Lakes system, and by surface area it is the second-largest lake in the world, behind only the Caspian Sea.
Superior borders Minnesota, Wisconsin, and Michigan in the United States, and Ontario in Canada. Its major ports include Duluth, Minnesota, at the lake’s western tip, and Thunder Bay, Ontario, on its northern shore. The lake is known for its rugged, rocky coastline, its dramatic cliffs, and its fierce storms. Its most famous shipwreck, the ore freighter Edmund Fitzgerald, which sank in a November storm in 1975, remains a symbol of the lake’s power.
Because Superior is so deep and cold, its water turns over very slowly. Scientists estimate that a drop of water entering Superior may remain there for nearly two centuries before flowing out. That slow rhythm is part of what makes the lake’s ecosystem so distinctive, and so sensitive to change.
Lake Michigan: The Only All-American Lake
Lake Michigan is the second-largest Great Lake by volume and the only one that lies entirely within the borders of the United States. It borders Wisconsin, Illinois, Indiana, and Michigan, and its shoreline touches some of America’s biggest cities, including Chicago and Milwaukee.
Michigan’s average depth is about 279 feet, with a maximum depth of roughly 923 feet. Its waters are connected to Lake Huron through the Straits of Mackinac, a narrow channel crossed by the Mackinac Bridge, one of the longest suspension bridges in the world. Because Michigan and Huron share the same water level, they are sometimes treated as one lake, Michigan-Huron, which by surface area would be the largest freshwater lake on Earth.
Lake Michigan is a recreational powerhouse. Its eastern shore is lined with sandy beaches and towering dunes, including the Sleeping Bear Dunes, while its western shore hosts busy ports and industrial cities. Millions of people live within a short drive of its shores, and its beaches draw summer visitors from across the Midwest.
Lake Huron: The Shoreline Champion
Lake Huron is the second-largest Great Lake by surface area, covering about 23,000 square miles, and the third-largest by volume. It borders Michigan in the United States and Ontario in Canada, and it is famous for one record in particular: counting its many islands, Huron has the longest shoreline of any of the five lakes.
Huron’s islands are a world unto themselves. Manitoulin Island, in the lake’s northern reaches, is the largest freshwater island in the world, a place of forests, lakes within the island, and small communities. The lake’s Georgian Bay, on its eastern side, is a maze of rocky islands and inlets beloved by boaters and cottagers.
Huron’s average depth is about 195 feet, with a maximum depth of roughly 750 feet. Its waters flow south through the St. Clair River into Lake St. Clair and then into Lake Erie, continuing the chain toward the Atlantic.
Lake Erie: The Shallow, Lively One
Lake Erie is the smallest Great Lake by volume and the shallowest by far, with an average depth of just 62 feet and a maximum depth of about 210 feet. That shallowness gives Erie a character all its own. Its waters warm up faster in summer than the other lakes, making it a favorite for swimming and boating, and its water turns over in just a few years, far faster than Superior’s centuries-long cycle.
Erie borders Michigan, Ohio, Pennsylvania, and New York in the United States, and Ontario in Canada. Its shoreline cities include Cleveland, Buffalo, Toledo, and Erie, Pennsylvania. The lake has historically been one of the most productive fisheries in the Great Lakes, and its walleye and yellow perch are prized by anglers.
Erie’s history is also a story of recovery. Decades ago, pollution severely damaged the lake, and it became a symbol of environmental decline. Since then, major cleanup efforts have brought real improvement, though the lake still faces challenges from agricultural runoff and harmful algal blooms. Erie remains a reminder that even the largest freshwater system on Earth needs active care.
Lake Ontario: The Small but Mighty Finale
Lake Ontario is the smallest Great Lake by surface area, at about 7,340 square miles, but it is far from the least important. It is the final lake in the chain, receiving water from Erie via the Niagara River and the famous Niagara Falls, then sending it onward into the St. Lawrence River toward the Atlantic Ocean.
Ontario is surprisingly deep for its size, with an average depth of about 283 feet and a maximum depth of roughly 802 feet, which means it holds more than three times as much water as the much larger-surfaced but far shallower Erie. It borders New York in the United States and Ontario in Canada, and its shoreline includes Toronto, Canada’s largest city, as well as Rochester, New York.
Because Ontario sits at the lowest elevation of the five lakes, it is the gateway between the Great Lakes and the ocean. Ships passing through the St. Lawrence Seaway system travel through Ontario on their way to and from the interior of the continent.
Why the Great Lakes Matter
The Great Lakes are far more than a scenic wonder. They are a working system that millions of people depend on every day.
First, they are a water supply. More than 40 million people in the United States and Canada depend on the Great Lakes for drinking water, and the lakes support agriculture, industry, and manufacturing across the region. The basin’s drainage area covers roughly 201,000 square miles, fed by thousands of streams and rivers. As the National Oceanic and Atmospheric Administration notes, the lakes contain roughly 20 percent of the world’s surface fresh water, making their health a matter of global significance.
Second, they are a shipping highway. The Great Lakes-St. Lawrence Seaway system allows ocean-going vessels to travel deep into the heart of North America, carrying iron ore, grain, coal, and manufactured goods. Ports from Duluth to Buffalo to Toronto handle cargo that feeds industries across two countries. The lakes have been a commercial artery since long before highways and railroads, and they remain one today.
Third, they are a wildlife treasure. The Great Lakes basin is home to thousands of species of plants and animals, from lake sturgeon and walleye to bald eagles, migratory waterfowl, and the wetlands that fringe the shores. The lakes’ coastal wetlands are among the most ecologically important in North America, providing breeding grounds for fish and stopover habitat for birds traveling the great migratory flyways.
Fourth, they are a climate force. The lakes moderate the climate of the surrounding region, keeping lakeshore areas cooler in summer and warmer in winter than inland areas. In winter, cold air passing over the relatively warm lake water produces lake-effect snow, a phenomenon famous in cities like Buffalo and Cleveland. In summer, lake breezes cool the shoreline and shape local weather.
Fun Facts That Put the Lakes in Perspective
The scale of the Great Lakes is hard to grasp until you put it in familiar terms. Their combined surface area of about 94,250 square miles is larger than the states of New York, New Jersey, Connecticut, Rhode Island, Massachusetts, Vermont, and New Hampshire combined. If their water were spread evenly across the contiguous United States, it would cover the country to a depth of nearly ten feet.
Superior alone is so large that its surface area exceeds that of South Carolina, and it contains more water than all the other Great Lakes combined. Lake Michigan is the largest lake entirely within a single country anywhere in the world. And Manitoulin Island in Lake Huron is the largest freshwater island on the planet, big enough to contain lakes of its own.
The lakes are also surprisingly young in geological terms, shaped by retreating glaciers only thousands of years ago. Before the glaciers, the region looked very different, and the lakes as we know them are the legacy of ice that once stood miles thick over the continent.
One more fact surprises many Americans: the Great Lakes are shared by two countries, eight states, and one Canadian province. The eight states are Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, and New York, and the province is Ontario. Managing a resource that crosses so many borders requires cooperation at every level, from local communities to international agreements between the United States and Canada.
Protecting a Treasure
The Great Lakes face real challenges. Invasive species such as zebra mussels and sea lamprey have reshaped lake ecosystems. Nutrient runoff fuels algal blooms, particularly in Lake Erie. Climate change is shifting water levels, ice cover, and water temperatures in ways scientists are still working to understand.
Yet the lakes also show what determined conservation can achieve. Binational agreements between the United States and Canada, cleanup programs, and decades of research by agencies like the EPA and NOAA have helped the lakes recover from some of their worst damage. The U.S. Geological Survey’s research on Great Lakes water levels tracks how lake levels have varied over thousands of years, helping planners understand the natural rhythms behind today’s changes. The story of the Great Lakes is not just one of natural wonder, but of stewardship: a reminder that the largest freshwater system on Earth is a shared inheritance, and a shared responsibility.
Whether you stand on a Lake Superior cliff watching a storm roll in, swim off a Lake Michigan beach on a summer evening, or watch a freighter glide through the St. Lawrence Seaway, the Great Lakes reward attention. They are, quite simply, one of America’s greatest natural facts, and they are worth knowing by name, by number, and by shore.
Frequently Asked Questions
What are the five Great Lakes?
The five Great Lakes are Superior, Michigan, Huron, Erie, and Ontario. They form the largest group of freshwater lakes on Earth by total area and contain roughly 20 percent of the world’s surface fresh water.
Which Great Lake is the largest?
Lake Superior is the largest by both surface area, about 31,700 square miles, and volume, about 2,900 cubic miles. It is also the deepest, with a maximum depth of about 1,330 feet, and the coldest of the five lakes.
Which states border the Great Lakes?
Eight U.S. states border the Great Lakes: Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, and New York. The Canadian province of Ontario also borders the lakes. Lake Michigan is the only Great Lake entirely within the United States.
Do the Great Lakes connect to the ocean?
Yes. Water flows through the chain of lakes from Superior to Ontario, then into the St. Lawrence River, which carries it to the Atlantic Ocean. The Great Lakes-St. Lawrence Seaway system also allows ships to travel between the lakes and the ocean.