The border between the United States and Canada is the longest continuous border in the world between any two sovereign countries. Furthermore, the province of Ontario has the longest border with the US of any Canadian province, though Alaska maintains the longest border with Canada of any US state. While most of the eastern part of the border was determined even before the US Revolutionary War (as the border between the colonies of Quebec and New York), the current border as-is was confirmed both by the Treaty of Paris in 1783 and the Jay Treaty of 1794. The former was mostly focussed on ending the war between Great Britain and virtually everyone else, while the latter intended to smoothen out remaining issues that lingered from the first treaty, and to generate a bit of good will between the two countries.

In the Jay Treaty, the British agreed to vacate eight forts they maintained within American territory, one of them being Fort Niagara, and to pay reparations to the US for damage to trading vessels, while the US paid off its pre-1775 debts. It also established a boundary commission to decide on the border, which was easily agreed in the north east but not so much in the north west; that latter commission was due to meet, but the War of 1812 proved to be a bit of a setback. After the war, the border was demilitarised as both countries became friendlier, and has remained that way ever since. ^__^

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