What does 54-40 or Fight refer to?

Answer 1

"54'40 or Fight" has been misidentified as Polk's campaign slogan in 1844. It appeared in January of 1846.

There was an Oregon border dispute between the British and America, and some people wanted the American border of the Oregon Territory to be extended to the line at 54'40. The border was set at the 49th Parallel with the cooperation of the Polk administration.