b) The Oregon boundary dispute

The slogan “Fifty-Four Forty or Fight!” in the 1840s referred to the Oregon boundary dispute between the United States and Great Britain. This phrase represented the northern latitude line, 54°40′, where many Americans, driven by the spirit of Manifest Destiny, believed the U.S. border should extend in the Oregon Territory. The dispute was a significant foreign policy challenge, reflecting the growing American expansionism and the desire to assert control over the Pacific Northwest. The eventual compromise set the border at the 49th parallel, shaping the modern boundaries of the U.S. and Canada.