Final answer:
The mid-1800s ideology of Manifest Destiny drove U.S. territorial expansion, persuaded by the belief that God ordained the nation's growth across the continent. It affected individual migrants and the nation by promoting Americanization and raising questions about freedom, republicanism, and the role of state in expansion. Economic pursuits also pressured expansion before official national integration.
Step-by-step explanation:
The ideology of Manifest Destiny significantly contributed to the mid-1800s drive for expansion in the United States. This concept was coined in the mid-1840s and was interpreted as a divine sanction for the westward territorial expansion of the United States. It suggested that the expansion across the continent was not just inevitable but also morally justified and ordained by God.
For individual migrants and the nation, Manifest Destiny underscored a sense of national mission and purpose. It built on earlier expansion efforts such as the Jeffersonian Louisiana Purchase and Jackson's Indian Removal program, revising America's national narrative to include a manifest future of spreading democratic institutions across the continent from "sea to shining sea". This ideology also resonated with the racial politics of the era; it was associated with the Americanization of indigenous peoples and Mexican residents in territories like Texas, Oregon, and California, often leading to conflict and dispossession.
Manifest Destiny did not just justify land expansion, but also had considerable implications for the nation, raising complex questions about freedom, republicanism, and the role of the state in expansion. The fear of overextension, changes in national security, and demographic shifts were among the significant concerns. The economic activities of private individuals pursuing commercial and agrarian ventures were significant pressures that often set the precedent for national expansion into new territories.