The United States, under the control of the Democratic Party, resolves the issue of Oregon’s northern border, set at the 49th parallel, with a treaty with Great Britain. In the northern United States, there was strong expectation that it would be set much further north: at 54.40. Disappointment was great, and it turned to anger when Southern interests were instead fully protected in the case of the Union’s southern borders, a case that would ultimately lead to war and victory against Mexico, with the annexation of California, Arizona, New Mexico, and Texas. Immediately thereafter, the question of extending slavery to the newly annexed states would erupt, a question strongly opposed by the North and strongly supported by the South. This would be just another of the many factors that, accumulating, would lead to the American Civil War.
