US President Donald Trump signed an executive order directing that Lake Ontario be renamed “Lake America,” amid an escalating trade dispute with Canada. Speaking at the White House, Trump said the change would take effect immediately. Canadian Prime Minister Mark Carney rejected the move, saying the lake’s name would always remain Lake Ontario.

The lake, the smallest of the five Great Lakes by area, lies along the US-Canada border and is connected to Ontario province and New York state. Carney said the nearly 400-year-old name predates both countries and comes from an Indigenous word meaning “the lake is beautiful, the lake is big.” He said on X that America was changing.

Trump’s order instructs the US Interior Department to update all entries for the lake in the federal geographic naming system within 30 days. It also directs all federal agencies to use “Lake America.” The order argues that the lake’s deepest point is on the US side and that the United States therefore claims most of its water volume.