What is the longest international border in the world?
In 1818, a U.S.-British agreement had established the border between Canada and the U.S. along the 49th parallel. Nowadays, the tension between the two countries is pretty non-existent but before the U.S. Civil War, the battle over who owned what seemed to be a never-ending issue.
In 1783, the border was set up on the 45th parallel as the northern border between New York and New Brunswick using the Great Lakes as a divider. As Americans headed west, the Great Lakes could no longer work as the great divide. In 1818, surveyors decided that one long line was the best way to split the countries and created it along the 49th parallel. It isn’t something the U.S. was exactly thrilled about but in the end, we got to keep Oregon and Canada got to keep their maple syrup. Source: The World Atlas