Donald Trump’s latest jab at Canada — threatening to rename Lake Ontario as “Lake America” amid the collapse of U.S.–Canada trade talks — has sparked fresh outrage on both sides of the border.
The insult from the U.S. President follows recent escalating rhetoric between Trump and Ontario Premier Doug Ford, who has accused Trump of abandoning long‑standing trade principles and treating Canada like a subordinate state.
Trump’s renaming threat arrives amid a bitter collapse in trade negotiations, which triggered 50 per cent U.S. tariffs on billions of dollars in Canadian goods and a promise from Canada to retaliate dollar‑for‑dollar.
However, behind the political theatre sits a lake with a history far older, deeper, and more complex than any modern dispute. Lake Ontario’s story stretches back hundreds of millions of years, shaped by ancient seas, mountain‑building collisions, and the last ice age. Here’s how Ontario — and its namesake lake — actually formed.
Long before Canada existed, the land that is now Ontario sat atop the Grenville geological province, a vast region of crystalline rock formed more than a billion years ago. These rocks — part of the Grenville orogeny — were shaped by continental collisions that built mountains rivalling the Himalayas.
Over time, erosion wore those mountains down, leaving behind the bedrock foundation of southern Ontario.
Roughly 20,000 years ago, the Laurentide Ice Sheet covered Ontario under kilometres of ice. As the glacier retreated, meltwater pooled in the Ontario basin, forming a series of early lakes — predecessors to what is known today as Lake Ontario.
Nearly 12,000 years ago, a retreating glacier opened the St. Lawrence Valley, allowing water to drain and creating a massive proglacial lake known as Lake Iroquois. As the land rebounded from the weight of the ice — a process called isostatic adjustment — water levels shifted, eventually stabilizing into the modern Lake Ontario.
For thousands of years before European arrival, the land that is now Ontario was home to Haudenosaunee, Anishinaabe, Huron‑Wendat, Cree, Algonquin, and other First Nations. The name Ontario comes from the Haudenosaunee word Ontarí:io, often translated as “great lake” or “beautiful water.”
The province was named for Lake Ontario when it was created in 1867 at Confederation. The lake’s name predates Canada, predates the United States, and predates European settlement entirely.
Presently, more than nine million people live along Lake Ontario’s Canadian shoreline. In other words: Lake Ontario already had a name long before any modern political leader — Canadian or American — entered the picture.
The U.S. cannot rename a bi-national lake on its own. Lake Ontario is governed jointly by Canada and the United States through a series of treaties, commissions, and bi-national agreements. Because the lake is shared, neither country can unilaterally rename it — not even a U.S. president.
The name “Lake Ontario” is recognized internationally, appears in federal legislation on both sides of the border, and is embedded in treaties dating back more than a century. If Trump wanted to rename the American side of the lake — even just informally — he would have to go through the U.S. Board on Geographic Names (BGN), a federal body responsible for naming natural features.
On the Canadian side, naming authority rests with the Geographical Names Board of Canada (GNBC), provincial naming authorities — in this case, Ontario’s Ministry of Natural Resources and Forestry and Indigenous communities — who are consulted on culturally significant names. Canada would have to agree to any change, which, simply put, is very unlikely.
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