Meaning of Fifty-four-forty or Fight

Fif'ty-four-for'ty or Fight'

Pronunciation: (fif'tē-fôr"fôr'tē, -fōr"-), [key]
— U.S. Hist. U.S. Hist.
  1. a slogan popular in 1846, esp. among Democrats, who asserted U.S. ownership of the entire Oregon country, including the part that Great Britain claimed between 49° and 54° 40prime; N latitude.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.