What is 54 40' or bust?

“54 40' or Bust” was a slogan used during the mid-19th century by expansionists in the United States advocating for the annexation of the Oregon Territory, which included land up to the latitude line of 54 degrees 40 minutes north. This phrase became particularly prominent during the 1844 presidential campaign of James K. Polk, reflecting the fervent desire for westward expansion. Ultimately, the boundary was settled at the 49th parallel in the Oregon Treaty of 1846, avoiding potential conflict with Britain over the disputed territory.