The religious belief that pushed Americans toward expansion is commonly referred to as Manifest Destiny. This 19th-century doctrine held that it was the destiny of the United States to expand its territory across the North American continent, a belief that was often entwined with a sense of divine purpose and mission. Manifest Destiny was used to justify American expansion and was characterized by a strong sense of nationalism and the belief that American civilization was superior and destined to spread.
While industrialization, the Frontier Thesis, and international exports played significant roles in American expansion, the specific religious motivation most closely associated with the drive for territorial growth is encapsulated in the idea of Manifest Destiny.