“Fifty Four, Forty or Fight!” was a slogan related to a line of latitude in reference to what?

The slogan "Fifty Four, Forty or Fight!" refers to the northern boundary that the United States sought to establish with Canada, specifically at the latitude of 54 degrees 40 minutes north. This slogan emerged in the context of the Oregon boundary dispute in the mid-19th century, where the U.S. and Great Britain were competing claims over the Oregon Territory, which included present-day Oregon, Washington, and parts of Idaho, Montana, and British Columbia.

The phrase captures the aggressive attitude of some American expansionists who were advocating for U.S. control of the area up to that latitude. Eventually, President James K. Polk, who campaigned on this slogan, negotiated a settlement with Britain which established the border at the 49th parallel in 1846, thus resolving the dispute peacefully. This historical context underscores the origins of the slogan as an expression of U.S. territorial ambitions in North America.