St. Lawrence River facts for kids

Kids Encyclopedia Facts

Quick facts for kids St. Lawrence River
Montréal-Est, Quebec
Great Lakes/St. Lawrence watershed
Other name(s)	Saint Lawrence River
Country	Canada, United States
Provinces	Ontario, Quebec
State	New York, Vermont
Physical characteristics
Main source	Lake Ontario Kingston, Ontario / Cape Vincent, New York 74.7 m (245 ft) 44°06′N 76°24′W / 44.100°N 76.400°W / 44.100; -76.400
River mouth	Gulf of St. Lawrence / Atlantic Ocean Quebec, Canada 0 m (0 ft) 49°30′N 64°30′W / 49.500°N 64.500°W / 49.500; -64.500
Length	500 km (310 mi) excluding the estuary. C. 928 kilometres if included. (St. Lawrence River–Lake Ontario–Niagara–Lake Erie–Detroit–Lake St. Clair–St. Clair–Lake Huron–St. Marys River–Lake Superior–St. Louis–North River: 3,058 km)
Width	Average width: 1–5 km (0.62–3.11 mi)
Depth	Minimum depth: 2 m (6 ft 7 in) (Fluvial Section) Maximum depth: 60 m (200 ft) (Quebec City)
Discharge (location 2)	Location: Tadoussac Average rate: (Period: 1962–1988)16,800 m³/s (590,000 cu ft/s)
Discharge (location 3)	Location: Quebec City Minimum rate: 8,600 m³/s (300,000 cu ft/s) Average rate: (Period: 1968–2023)12,500 m³/s (440,000 cu ft/s) Maximum rate: 22,766 m³/s (804,000 cu ft/s)
Discharge (location 4)	Location: Montreal Average rate: (Period: 1971–2000)10,063.3 m³/s (355,380 cu ft/s)
Discharge (location 5)	Location: Cornwall Average rate: (1861–2019)7,060 m³/s (249,000 cu ft/s)
Basin features
Progression	Gulf of St. Lawrence
River system	St. Lawrence River
Basin size	1,344,200 km² (519,000 sq mi) (Pointe-des-Monts: 1,271,547.4 km²)

The St. Lawrence River (called Fleuve Saint-Laurent in French) is a huge international river in North America. It connects the amazing Great Lakes to the Atlantic Ocean. The river flows northeast from Lake Ontario through parts of Canada (Ontario and Quebec) and the United States (New York). A section of the river even forms part of the border between Canada and the U.S.

This mighty river is the main way water leaves the Great Lakes. It has the second-highest water flow of any river in North America, right after the Mississippi River. Its wide mouth, called an estuary, is considered one of the largest in the world. Along its path, you can find cool places like the Thousand Islands (with 1,864 islands!), a special marine park where you can see whales, and the unique rock formations of the Mingan Archipelago.

For a very long time, the St. Lawrence River has been a vital travel route for Indigenous communities. It has also been super important in the history of Canada and helped big cities like Montreal and Quebec City grow. Today, it's still a busy shipping lane thanks to the St. Lawrence Seaway. This system of locks and canals allows large ships from all over the world to reach ports deep inside the continent.

Naming the St. Lawrence River

Ancient Names from First Nations

For many centuries, different Indigenous groups had their own names for this important river. These names often described its features or its role in their lives. For example, the Algonquin people called it "the Walking Path" or "Large Water River."

Here are some of the names Indigenous peoples used:

The Innu-aimun people called it Wepistukujaw Sipo or Wepìstùkwiyaht sīpu.
The Abenaki knew it as Moliantegok ("Montréal River") or Kchitegw ("Great River").
In the Mohawk language, it was called Roiatatokenti or Kaniatarowanénhne.
The Tuscarora people used Kahnawáˀkye or Kaniatarowanenneh ("Big Water Current").
The Wendat Nation referred to it as Lada8anna or Laooendaooena.
The Atikamekw people called it Micta sipi ("Huge River").

How Europeans Named the River

When French explorers arrived in the 1500s, they also gave the river names like Grand fleuve de Hochelaga and Grande rivière du Canada. The words fleuve and rivière both mean river in French.

The name we use today, St. Lawrence, came from Jacques Cartier. In 1535, he sailed into the bay on August 10th, which was the feast day for Saint Lawrence. So, he named the bay the Gulf of Saint Lawrence. Later, in 1604, Samuel de Champlain used the name Fleuve sainct Laurens for the river on his maps and in his writings, and that name stuck!

River Geography and Features

Boats racing on the St. Lawrence River in 2000

A cross marking where Jacques Cartier landed in 1535, Trois-Rivières

An ancient sea once covered this area

Winter Ice on the River

During winter, usually starting in December, the St. Lawrence River between Montreal and Quebec City begins to freeze. Winds and currents push this ice towards the wider mouth of the river. By January and February, ice can cover the entire Gulf of St. Lawrence.

This ice actually helps ships navigate! It stops big waves from forming and prevents ice from building up on the ships themselves.

The River's Journey and Watershed

The St. Lawrence River was formed after a large body of water called the Champlain Sea drained away. This happened about 13,000 to 10,000 years ago. The land slowly rose after the last ice age, causing the sea to shrink.

The St. Lawrence River officially starts where Lake Ontario flows out. It then passes by many towns and cities like Kingston, Brockville, Cornwall, Montreal, Trois-Rivières, and Quebec City. Finally, it empties into the Gulf of St. Lawrence, which is often called the world's largest estuary. The river becomes tidal (meaning its water level changes with the ocean's tides) around Quebec City.

The entire St. Lawrence River system, from its farthest source to its mouth, stretches about 3,058 kilometers (1,900 miles). Just the section from Lake Ontario is about 500 kilometers (310 miles) long. The very farthest source is the North River in Minnesota, U.S.

The river's drainage area is huge, covering about 1,344,200 square kilometers (519,000 square miles). This area includes all the Great Lakes, which are the largest system of freshwater lakes in the world! The basin reaches across parts of Canada (Ontario and Quebec) and many U.S. states like New York, Michigan, and Ohio.

Lakes and Islands Along the Way

The St. Lawrence River flows through several lakes, including Lake Saint Francis, Lake Saint-Louis, and Lake Saint Pierre. It also features amazing groups of islands, called archipelagoes.

Some of these include:

The Thousand Islands near Alexandria Bay, New York and Kingston, Ontario.
The Hochelaga Archipelago, which has the Island of Montreal and Île Jésus.
The Lake St. Pierre Archipelago, recognized by UNESCO for its natural importance.
The smaller Mingan Archipelago.

Other notable islands are Île d'Orléans near Quebec City and Anticosti Island in the gulf. The St. Lawrence is the second-longest river in Canada.

Rivers Joining the St. Lawrence

Many other rivers flow into the St. Lawrence, adding to its mighty waters. These include Lake Champlain and the Ottawa, Richelieu, Saint-Maurice, Saint-François, Chaudière, and Saguenay rivers.

River's Deep History and Geology

The St. Lawrence River flows through an area where the Earth's crust is still active. This means there are faults (cracks in the Earth) that can sometimes move, causing small earthquakes. These faults are part of the Saint Lawrence rift system, formed long ago when continents pulled apart.

Geologists in the U.S. see the St. Lawrence Valley as part of the larger Appalachian region. However, in Canada, where most of the valley lies, it's considered a separate area called the St. Lawrence Lowlands.

The Many Names of the River's Source

The very beginning of the St. Lawrence River system is considered to be the North River in Minnesota. Because the water travels through so many lakes and connecting rivers, its name changes several times along the way.

From its source to the mouth, the main parts of the river system are:

The St. Lawrence River itself also flows through Lake Saint-Louis and Lake Saint-Pierre in Quebec.

Looking downstream: Quebec City (left), St. Lawrence River, Île d'Orléans (center), Lévis (right), Laurentian Mountains (background).

River's Water Flow

The St. Lawrence River is a massive waterway, and the amount of water flowing through it changes throughout the year. Scientists measure this flow in different places.

For example, near Quebec City, the river's average flow is about 12,500 cubic meters (441,400 cubic feet) of water every second. Further downstream, closer to the ocean at Pointe-des-Monts, the average flow increases to about 17,600 cubic meters (621,500 cubic feet) per second. This shows just how much water the St. Lawrence carries from the Great Lakes to the Atlantic Ocean!

Amazing Wildlife of the St. Lawrence

The St. Lawrence River and its estuary are home to an incredible variety of plants and animals. This rich biodiversity makes it a very special place!

Here's a glimpse of the life found here:

19 different kinds of marine mammals, like whales and seals.
Over 230 species of birds, from tiny songbirds to large seabirds.
Nearly 35 types of amphibians and reptiles.
200 species of fish, including both freshwater and saltwater kinds, and even 19 types of sharks and rays!
About 2,200 different invertebrates (animals without backbones) in the estuary and gulf, such as sponges, jellyfish, corals, and crustaceans.
Nearly 2,000 types of vascular plants (plants with roots, stems, and leaves).

Marine Mammals and Their Life Cycle

Fin whales swimming near Tadoussac

Large marine mammals, especially whales, are a huge part of the St. Lawrence ecosystem. People who fish, work on ships, or study nature are all fascinated by these giants. Scientists from Canada and around the world constantly study them.

Thirteen different types of cetaceans (whales and dolphins) visit the waters of the St. Lawrence estuary and the Gulf of St. Lawrence. These include:

History of the St. Lawrence River

A 1543 map showing Jacques Cartier's discoveries (c. 1909)

Basque settlements from the 1500s and 1600s

A watercolor from 1792 showing a bend in the St. Lawrence River in Quebec

First Peoples and Their Homelands

The St. Lawrence River has always been a central pathway for many Indigenous nations. It flows through or next to their traditional lands. For example, the river borders Mi'kma'ki to the south and Nitassinan (the Innu homeland) to the north.

Further along, it passes through the homelands of the Maliseet, Penobscot, and Abenaki peoples. The river also flows through the lands of the St. Lawrence Iroquoians and three of the six nations of the Haudenosaunee: the Mohawk, Oneida, and Onondaga.

In the early 1600s, the Wendat Nation moved to an area called fr:Nionwentsïo, which includes parts of both sides of the river. Other nations like the Atikamekw and Algonquin also have homelands along the St. Lawrence.

European Explorers Arrive

The first Europeans to explore the Gulf of St. Lawrence were the Norse in the 11th century. Later, in the 15th and early 16th centuries, explorers like John Cabot and the Corte-Real brothers also visited.

The first European known to sail up the St. Lawrence River itself was Jacques Cartier in 1535. He named the gulf after Saint Lawrence because he arrived on his feast day. At that time, the riverbanks were home to the St. Lawrence Iroquoians. The St. Lawrence River is one of the oldest European place-names still used in the U.S. today.

Early European Settlements

The earliest regular European visitors were the Basques. From the early 1500s, they came to the St. Lawrence Gulf and River to hunt whales. These Basque whalers and fishermen traded with Indigenous Americans and set up small settlements. You can still find traces of their presence along the eastern Canadian coast and deep into the St. Lawrence River.

Until the early 1600s, the French called the river Rivière du Canada. The St. Lawrence River became the main route for French explorers, like Samuel de Champlain, to explore the interior of North America.

Colonial Control and Conflicts

Controlling the St. Lawrence River was very important for the British during the Seven Years' War. They wanted to capture New France from the French. After taking Louisbourg in 1758, the British sailed up the river to Quebec City in 1759, using maps made by James Cook. British troops used the river to attack Quebec City from the west, leading to their victory at the Battle of the Plains of Abraham. The river was also used by the British to defend Quebec City from a French siege in 1760.

In 1809, the first steamboat on the St. Lawrence, called the Accommodation, began carrying passengers between Montreal and Quebec City. This made travel much faster and easier.

Because of the difficult Lachine Rapids, ships could only sail so far up the river. To solve this, the Lachine Canal was opened in 1825, allowing ships to bypass the rapids. Later, a much larger system of canals and locks, called the St. Lawrence Seaway, was opened in 1959. This amazing engineering feat allows large ocean-going ships to travel all the way to Lake Superior in the Great Lakes.

Modern River Use and Protection

For many decades, factories like Alcoa, Reynolds Metals Company, and General Motors operated along the St. Lawrence River. These factories released certain substances into the river and surrounding areas.

During World War II, the Battle of the St. Lawrence took place. German U-boats (submarines) attacked ships in the lower St. Lawrence River and the Gulf of St. Lawrence. Several merchant ships and Canadian warships were sunk during these battles.

In the late 1970s, a successful environmental campaign called "Save the River" helped protect the St. Lawrence. This campaign worked to stop development plans that could harm the river.