Final answer:
Manifest Destiny was a 19th-century doctrine that the US was destined to expand across North America, justified by a sense of mission and divine right. It led to significant territorial acquisitions but also increased domestic and international tensions.
Step-by-step explanation:
Manifest Destiny
The term Manifest Destiny encapsulates the 19th-century doctrine or belief that the expansion of the US throughout the American continents was both justified and inevitable. It provided a religious and moral justification for the expropriation of land, asserting that the United States had a divine right to expand its territory across North America 'from sea to shining sea'. This belief was a driving force behind the westward colonial expansion by Europeans and the displacement of Native American populations.
Originated by journalist John O'Sullivan in 1845, Manifest Destiny played a critical role in shaping the national agenda and foreign policy. It was used to justify the annexation of territories, such as Texas and Oregon, and heavily influenced the U.S. decision to go to war with Mexico, leading to the acquisition of territories in the current Southwest, including California. While Manifest Destiny was a popular concept, it also exacerbated tensions between free and slave states and affected international relations, particularly with Mexico and European powers.