What did the battle cry “fifty-four forty or fight” mean?

The battle cry “fifty-four forty or fight” mean was the slogan of U.S. expansionists who wanted to fix the boundary of the Oregon country (the Pacific Northwest) at latitude 54° 40′ N., in the middle of what is now British Columbia in Canada.

The belligerent slogan was associated with the presidential campaign of James K. Polk in 1844.

Despite the bluster, Polk’s administration agreed to fix the boundary at 49° N. in 1846.