Related: episode 653 of 99% Invisible mentions Peace Arch Park, which is along the US-Canada border in Blaine, Washington, and Surrey, British Columbia. Anyone from either country can enter the park and mingle with people from the other country. There's supposedly strong incentive, because of a treaty from the War of 1812, for both countries to keep their side of the park open:
If Canada broke the treaty, in theory, the U.S. could lay claim to parts of Ontario and Quebec. And if America broke it, Canada could get parts of Maine, Michigan, and Wisconsin. So, basically, North American geography as we know it is contingent on this early 1800s treaty remaining in effect.
The podcast was from December -- an eternity ago in these interesting times -- and I don't know whether anything has changed since then.
https://99percentinvisible.org/episode/653-beyond-the-99-inv...
We went to Peace Arch Park several times during COVID to visit relatives in Canada. And then I noticed the tents on the eastern edge of the park. What's that all about? I called it the End Zone. Couples separated by the border would meet there. One park ranger said he saw things he couldn't unsee...
I have a hard time believing that Canada would ever get parts of the US if America broke this. Even if the signed document included unambiguous promises written in the verified DNA of a famous American president or other extravagances
This is a good story, but you can read both the Treaty of Ghent (which ended the War of 1812 while keeping the US-Canada border the same) and Rush-Bagot (which restricted naval fleets on the Great Lakes and Lake Champlain). Neither document states anything about the border needing to remain open or without barriers.
The podcast's transcript suggests that their source for this is https://www.cbc.ca/news/canada/british-columbia/peace-arch-u.... The person confidently claiming that any closure of the park would result in catastrophe is an immigration lawyer, not a historian:
"Saunders said the treaty stipulates there could not be any boundaries or physical barriers erected on the northern border of the U.S. — and if either side violated that treaty — the boundaries revert back to pre-treaty."
Since the Treaty of Ghent restored the pre-War of 1812 borders of both the United States and Canada, this doesn't make any sense. Canadian historian C. P. Stacey states that the period after the War of 1812 actually saw more border fortification than the years before (https://www.jstor.org/stable/1840618).
I mentioned that the idea that a 19th century treaty keeps the US-Canada border demilitarized was a good story, but I think the truth is an even better one: that the border is demilitarized because both countries know that they can trust their neighbor. Let's hope it stays that way.