I. Manifest Destiny
The concept of manifest destiny seeped into the American consciousness during the early settlement of the United States. Even before British Captain James Cook explored the northwest coast of North America by sea in 1778, explorers had hoped to find a passage to the Pacific through the waterways of the American continent. If found, this would save them months of dangerous sailing around the southern tip of South America in order to reach the fabled markets of the Far East. Acting on a mandate from President Thomas Jefferson to find a direct & practicable water communication across this continent, for the purposes of commerce with Asia, Meriwether Lewis and William Clark in 1805 reached the Pacific Ocean at the mouth of the Columbia River in Oregon at a fort later named Astoria.
During the debates over the Oregon Territory and the war with Mexico in the 1840s, America's destiny became even clearer to policy and opinion makers. The phrase, manifest destiny, first given voice in 1845, embraced achieving a new U.S. western boundary--the Pacific Ocean--and developing the land in between. Advocating a treaty with England to cede the Oregon Territory to the United States, newspaper editor John L. O'Sullivan wrote that America's claim to the land was by the right of our manifest destiny to overspread and to possess the whole of the continent which Providence has given us for the development of the great experiment of liberty and federated self government entrusted to us. The slogan caught on during the Mexican War and became the subject of debate in newspapers and political venues for years afterward.
Manifest destiny incorporated two interrelated components: the expansionist mission to settle the land to the Pacific shore, eventually establishing commerce with Asia, and the belief in Anglo-Saxon racial superiority.