What is the fifty four forty of fight?

The phrase "Fifty-Four Forty or Fight!" refers to a slogan used in the 1840s during the Oregon boundary dispute between the United States and Great Britain. It represented the boundary line at latitude 54°40′ north, which American expansionists claimed as the northern limit of the Oregon Territory. The slogan encapsulated the strong desire for U.S. expansion westward and became a rallying cry for those advocating for the annexation of Oregon. Ultimately, the dispute was settled diplomatically, and the border was established at the 49th parallel in 1846.