Final answer:
Manifest Destiny was a 19th-century doctrine that the United States was destined to expand across North America, spreading its democratic ideals and displacing indigenous populations in the process.
Step-by-step explanation:
The concept of Manifest Destiny is a historical belief that the United States was preordained to expand its territory and influence across North America. This notion, popularized in the 1840s, was believed to be a divine right and an inevitable process symbolized by the phrase 'from sea to shining sea.' As settlers moved westward, claiming land and spreading American institutions, they often conflicted with the preexisting populations, particularly Native Americans and Mexicans. The impact of Manifest Destiny went beyond mere land acquisition; it was a project of cultural assimilation or Americanization that promised to spread democratic ideals and freedom. However, it also encompassed more troubling aspects, such as the justification for conquest and the displacement of Native Americans, Mexicans, and other non-European groups.
The excerpt from 'The Great Nation of Futurity' by John O'Sullivan reflects the idea of Manifest Destiny as a blend of national destiny, divine providence, and virtue. It suggests that America's expansion was not only inevitable but also a moral obligation to spread its principles. Such expansion, however, was in direct conflict with the rights and ways of life of the Indigenous populations, whose reactions ranged from resistance to negotiation and, often, forced removal.