Original copy of the Treaty as kept by the U.S. National Archives.
Joint control steadily grew less tolerable for both sides. After a British minister rejected U.S. PresidentJames K. Polk's offer to settle the boundary at the 49th parallel north, Democraticexpansionists militantly called for the annexation of the entire region up to Parallel 54°40′ north, the southern limit of Russian America as established by parallel treaties between the Russian Empire and the United States (1824) and Britain (1825). However, after the outbreak of the Mexican-American War in April 1846 diverted U.S. attention and military resources, a compromise was reached in the ongoing negotiations in Washington, D.C., and the matter was settled by the Polk administration (to the dismay of its own party's militant hardliners) to avoid a two-war situation and the third war with the formidable military strength of Great Britain in less than 70 years.
The dispute over the San Juan Islands, mentioned above, lasted until an arbitration agreement in 1871. The treaty also had the unintended consequence of putting what became Point Roberts, Washington on the "wrong" side of the border. A peninsula jutting south from Canada into Boundary Bay, the agreement made the land south of the 49th parallel a separate fragment of the United States.
^officially titled the Treaty between Her Majesty and the United States of America, for the Settlement of the Oregon Boundary and styled in the United States as the Treaty with Great Britain, in Regard to Limits Westward of the Rocky Mountains, and also known as the Buchanan-Pakenham (or Packenham) Treaty or (sharing the name with several other unrelated treaties) the Treaty of Washington