US President Donald Trump on Thursday (August 27) signed an executive order to rename Lake Ontario, situated on the US-Canada border, as “Lake America”. The order said the lake was a “tremendous asset to the United States and part of our Nation’s heritage.”

In response, Canadian Prime Minister Mark Carney wrote in a post on X that the name Ontario (also the name of a Canadian province) comes from the indigenous Wendat people.

“The name is more than 400 years old, predating both the Confederation of Canada and the Declaration of Independence of the United States of America. We know that America is changing. Their trading relationships, their foreign policies, their national monuments, their hydronyms. Canadians also know that naming reality means calling it Lake Ontario – then, now and always,” he wrote.

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What’s behind Trump’s order, and can countries unilaterally change the names of water bodies? In Trump’s case, there is precedent for the move, which also involved a neighbouring nation.

What is Lake Ontario, and why is Trump renaming it?

Lake Ontario is part of the Great Lakes system, along with Lake Superior, Michigan, Huron and Erie, spanning the US-Canada border. According to the US National Ocean and Atmospheric Administration (NOAA), the lakes system holds about 90% of the freshwater in the US and approximately 20% of the world’s freshwater supply. Forty million people across the two countries depend on it for clean drinking water.

Lake Ontario. (Google Maps)

In his executive order, Trump cited a range of reasons for the decision — including the US’s investments in the lake to keep it open for free shipping, Canada spending comparatively less on it, and the lake’s history as an “asset to American exploration, settlement, commerce, and defense.”

But more pressingly, it comes amid heightened trade tensions between the countries. Trade talks collapsed last week and led to the US imposing tariffs on Canada, with Carney promising to match them “dollar for dollar” against American imports. The US is Canada’s largest trading partner, while Canada is the US’s second-largest trading partner.

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So how will Lake Ontario be addressed now?

The name change will apply to how the US officially refers to the lake, but it will not affect how Canada or the rest of the world choose to call it. No single global organisation is tasked with ensuring uniformity among names of water bodies, and the decision to use a certain name is often based on historical precedent.

In a social media post, Trump stated that the US Geological Survey was officially changing the name to have it reflect in all official USGS electronic documents.

This is not the first time that disagreements over trade and other issues have prompted Trump to use nomenclature as a tool.

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In January 2025, the day Trump took office in his second term, he signed a slew of executive orders. These included one on renaming the Gulf of Mexico as the Gulf of America, amid tensions with Mexico over immigration and tariffs. According to Reuters, it took about two weeks for the US government to update the official federal nomenclature to reflect those changes. The change was also reflected on Google Maps.

How Google Maps names disputed features.

According to Google, the names seen on Maps are based on information such as a user’s country location and phone operating system (e.g., iOS and Android). Users in Mexico saw “Gulf of Mexico” on Maps while those in the US saw “Gulf of America”. For other users, both names are visible. This is seen in some other features with disputed names, too, like the Persian Gulf, which is followed by “Arabian Gulf” in brackets on Google Maps.