What Makes It Bizarre?
While it is a huge stretch of land, that’s not really what makes it bizarre. Not even the fact that it’s unprotected makes it all that strange; there are big, undefended borders in lots of places, although it’s getting rarer all the time.
In order to understand why the border is so weird, we need to go back in time to see how it was created.
Source: The Canada-U.S. Border
After the 7 Years War
That’s what happens when you try to forge a line between two countries that weren’t yet fully developed, in a land that was not yet fully explored. The border between the nations actually predates the nations themselves. After the 7 Years War, France renounced its possessions in North America in 1763.
They gave all of what would eventually become Canada to the British, but kept the sugar-producing island of Guadalupe – they thought it was much more valuable than Canada, which Voltaire dismissed as “a few acres of snow.”
The next major border agreement came with the Treaty of Paris in 1783, after the American Revolution. American colonists made some efforts to take Canada from the British during the revolution but were repelled.