First, Manifest Destiny was coined by newspaper editor, John O'Sullivan, and was effectively used to Justify many means of acquiring land in America after 1845. There are numerous examples as to how this was used, for instance, the Oregon treaty. Citizens began to migrate westward in search of new settlements, and many were found to be settling in places such as California, New Mexico, Oregon and Texas. Oregon at the time was owned by Great Britain, and when James K. Polk won the presidency in 1844, he began working to ultimately bring Texas into the Union as a slave state, and through the Oregon Treaty of 1846 and many negotiations with Great Britain, brought Oregon into the Union as a free state. James K. Polk declared war on Mexico because
