Final answer:
Polk was influenced by the issue of Oregon in 1844 by settling with Britain on accepting the 49th parallel as the boundary line between the U.S. and Britain for Oregon Territory. This decision allowed the U.S. to focus on preparing for war with Mexico.
Step-by-step explanation:
Upon taking office, James K. Polk began talks with Britain about the issue of Oregon. Expansionists demanded that the United States take all of Oregon Territory, but Polk was willing to accept a boundary line along the 49th parallel, splitting Oregon between the U.S. and Britain. By accepting less of Oregon, Polk and the nation could focus on preparing for the coming war with Mexico. This compromise displeased some expansionists, but others saw its pragmatism.