(The Center Square) – President Donald Trump said he's giving "serious consideration" to renaming Lake Ontario "Lake America" amid trade tensions with Canada that could test a 1989 agreement on naming features the two countries share.

Trump made the comment Tuesday in a post on Truth Social, writing that the U.S. "is giving serious consideration to changing the name of Lake Ontario to Lake America in that we don't expect to be doing much business with Ontario any longer."

The post came as the trade war between the two countries escalated. The U.S. imposed 50% tariffs on about $20 billion in Canadian goods over the weekend after talks collapsed.

On Tuesday, Finance Minister François-Philippe Champagne announced Canada would match the U.S. duties "dollar for dollar, rate for rate," with counter-tariffs of 15%, 25% and 50% on U.S. goods taking effect Sept. 8, alongside a support package for affected workers and businesses.

Ontario Premier Doug Ford, whom Trump appeared to be answering, threatened Monday to cut the province's electricity exports to the U.S.

Trump renamed the Gulf of Mexico earlier in his second term, a move that frustrated America's southern neighbor, Mexico. In January 2025, the U.S. president signed an executive order changing the Gulf of Mexico to the "Gulf of America," directing the Interior secretary to make the change through the U.S. Board on Geographic Names and update the federal Geographic Names Information System. The change took a secretarial order and about three weeks to appear in the federal database.

But the Gulf precedent also shows the limits of a presidential renaming. Names set by the Board on Geographic Names apply only to federal documents, according to a Congressional Research Service analysis of the Gulf change. They do not bind U.S. states, private mapmakers such as Google or Apple, or foreign governments, and a United Nations naming convention allows each country to keep its own name for a shared feature. That means "Lake Ontario" and "Lake America" could both appear on maps.

Lake Ontario also raises an obstacle the Gulf did not. Board policy requires that proposals to name features crossing the U.S.-Canada border be coordinated with Canada's naming authority under a 1989 agreement on the treatment of shared geographic names, according to the Congressional Research Service. There is no equivalent agreement with Mexico. Lake Ontario, bordered by New York to the south and the Canadian province of Ontario to the north, is such a feature. That means a unilateral U.S. renaming could bypass the coordination the agreement calls for.

The Interior Department did not immediately respond to questions about whether it or the Board on Geographic Names has taken any step to rename Lake Ontario, or how it views the 1989 agreement's application.

Natural Resources Canada, which houses the Geographical Names Board of Canada, did not immediately respond to questions about whether U.S. authorities have sought to coordinate on a name change, or what the 1989 agreement requires when one country moves to rename a shared feature.

The lake's name long predates the dispute, though its exact meaning is uncertain. The word "Ontario" comes from an Iroquoian language. Natural Resources Canada traces it to the Iroquois "kanadario," meaning "sparkling water," while other sources render it from Wyandot as "beautiful lake." Its official Canadian name is set by the province of Ontario, not the federal government in Ottawa, according to the Canadian Geographical Names Database.

A federal renaming would likely be inexpensive, at least on paper. When the U.S. House moved last year to codify the Gulf of America name, the Congressional Budget Office estimated that updating federal documents and maps would cost less than $500,000. But CBO's work on other renaming efforts shows costs depend on how far an agency takes it.

Reviewing the administration's adoption of "Department of War" as a secondary name for the Defense Department, CBO put the range at a few million dollars to as much as $125 million, noting the department "declined to provide information" on its plans.

The issue could also reach beyond Washington: North Carolina spent nearly $200,000 to change highway signs when Fort Bragg became Fort Liberty, and about the same again to change it back, according to CBO.

As of Tuesday, Trump had signed no executive order, and the proposal existed only as a social media post.