St. Lawrence River Facts For Kids

The St. Lawrence River is one of North America's mightiest waterways. It connects the huge Great Lakes to the wide North Atlantic Ocean. Flowing northeast from Lake Ontario, this river carries fresh water from the heart of the continent to the salty sea. For part of its journey, it marks the border between Canada and the United States, linking two friendly neighbors.

This amazing river is the main drain for the Great Lakes Basin, a giant area of land where rainwater gathers. Near its mouth, it widens into the world's largest estuary—a special place where river meets sea and ocean water mixes in. Cool spots along the way include the rocky Thousand Islands, a watery playground of tiny isles, and nearby marine parks full of sea life.

People have traveled and lived by the St. Lawrence for thousands of years because it offers food, transport, and beauty.

The St. Lawrence River starts at Lake Ontario and winds northeast for about 1,900 miles, including its wide estuary. Without the estuary, it's around 300 miles long. It flows past busy towns in Ontario and Quebec in Canada, and even touches New York State in the U.S.

The river shares the Canada-U.S. border for a stretch, like a natural line between friends. Around Quebec City, it turns tidal—meaning ocean waves push water upriver twice a day. Then it opens into the Gulf of St. Lawrence, a big arm of the Atlantic Ocean.

Along the way, you'll see islands, forests, and cities. Ships sail its waters, carrying goods from far away because the path is deep and steady.

The watershed of the St. Lawrence is like a huge bowl of land—over a million square kilometers big! Rain and melted snow from parts of eight U.S. states and seven Canadian provinces flow into it. Most of the land is in Canada, but Michigan in the U.S. sends a lot of water too. The farthest drops start way up in Minnesota.

Long ago, after the last Ice Age about 10,000 years back, a giant sea called the Champlain Sea filled this area. As ice melted and land bounced back up, the sea shrank, carving the river we know today. That slow lift still happens a tiny bit each year.

Near Lake Ontario, the Thousand Islands dot the river's start, formed by ancient rocks and water.

Long before Europeans came, First Nations people gave the St. Lawrence many names in their languages, honoring its power and gifts.

In 1535, French explorer Jacques Cartier sailed up it and named it for Saint Lawrence, a holy figure. His feast day was August 10, the day he arrived. Later, Samuel de Champlain wrote it as "Grande riviere de sainct Laurens" on maps around 1604.

Today, English speakers call it the St. Lawrence River, while in French it's fleuve Saint-Laurent—fleuve means a big river that reaches the sea. The name stuck because explorers loved its beauty and size.

Long before Europeans arrived, many Indigenous peoples called the lands around the St. Lawrence River home. These groups lived in harmony with the river, fishing its waters and using its path for travel. In the east, near the Gulf of St. Lawrence, were the Mi'kmaq in Mi'kma'ki and Innu in Nitassinan. As the river flowed west, it passed through territories of the Maliseet, Penobscot, and Abenaki.

Further upstream, the St. Lawrence Iroquoians made their homes along the shores. Nearby were Haudenosaunee nations like the Mohawk, and the Wendat people settled in areas called Wendake. On the north side lived the Atikamekw and Anishinaabe groups, such as the Algonquin. The river connected these communities, sharing stories, trade, and ways of life for thousands of years.

Today, these peoples' descendants still honor their deep ties to the St. Lawrence.

Explorers from faraway lands were drawn to the St. Lawrence River centuries ago. Long before others, Norse sailors may have reached the Gulf of St. Lawrence around the 11th century. Later, in the 1400s and 1500s, mariners like John Cabot and the Corte-Real brothers sailed nearby coasts.

The big moment came with Jacques Cartier, a French explorer. In 1534, he entered the gulf and, the next year, boldly sailed up the river. On August 10—Saint Lawrence's feast day—he named the gulf after the saint. Cartier's trips opened the river to more Europeans, leading to settlements and new maps.

These journeys changed history, blending Indigenous knowledge with European maps.

Tributaries are smaller rivers that flow into the St. Lawrence, making it stronger and wider. They bring fresh water from forests, lakes, and hills all around. Some of the biggest ones include the Ottawa River from the northwest, the Saguenay from the north, and the Richelieu from the south.

The Saint-Maurice rushes down from northern mountains, while the Saint-François and Chaudière add water from the south. These tributaries create rich habitats for fish and wildlife. For example, the Ottawa is super long and carries water from huge areas, helping boats travel far inland.

Together, they feed the St. Lawrence like branches on a mighty tree, supporting life along its whole path.

The St. Lawrence River's weather changes with the seasons, just like a big backyard playground. In summer, it's warm and busy with boats zipping along sunny waters. Fall brings colorful leaves and cooler breezes.

Winter is chilly! Ice starts forming in December between cities like Montreal and Quebec City, then spreads to the gulf by January. This ice blanket smooths waves and helps ships by stopping frost on their hulls. Spring melts it all, causing fast floods of water.

These shifts affect animals, fish, and people who fish or sail. Each season shows the river's power and beauty.