"Manifest Destiny" refers to the 19th-century belief that the expansion of the United States across North America was both justified and inevitable. Advocates viewed it as a divine right and duty to spread democracy and capitalism, which they believed would lead to progress and civilization. This ideology fueled territorial expansion, justified acts such as westward migration, and was often used to rationalize the displacement of Native Americans and conflicts with Mexico. Manifest Destiny played a significant role in shaping U.S. policies and identity, influencing events like the annexation of Texas and the Oregon Trail migration, while also inflaming tensions over slavery.