"Manifest Destiny" was a phrase first introduced by John L. O'Sullivan in 1845. This term refers to the belief that Americans had the God given right to expand from the Atlantic to the Pacific. From 1830 to 1850, the United States continued their quest of expansion through to the Pacific included the acquisition of Oregon, Texas, and California. The United States favored the negotiation process but when it fails and if provoked they would result to war.

To begin with, Oregon was a territory that belonged to Spain, Russia, Great Britain, and the United States. In the Transcontinental (or Adams-Onís) Treaty of 1819, Spain gave up their claims of Oregon north of the forty-second parallel. In the United States and Great Britain who had joint-occupation of Oregon with an original agreement signed in 1818. In the election of 1844 James K. Polk's campaign slogan "54°40' or fight" referring that the United States would...