During the Civil War era, "Manifest Destiny" referred to the widely held belief that the United States was destined to expand its territory across North America.

This ideology justified westward expansion and was often used to promote the annexation of land, including Texas and Oregon. Proponents believed it was their divine right to spread American democracy and civilization. However, this belief also contributed to conflicts over slavery in new territories, exacerbating sectional tensions and ultimately playing a significant role in the lead-up to the Civil War.