The concept that the United States (and, more especially, the white Anglo-Saxon race inside it) was destined to expand across the continent was known as "Manifest Destiny" in the nineteenth century. In the 1840s, Democrats coined the phrase to justify the war with Mexico. Whigs primarily opposed the concept, and it fell out of favor by the mid-nineteenth century. Manifest destiny proponents believed that expansion was not only wise, but also obvious and could not be stopped.
The idea in the United States' divine right to extend over and conquer the continent was known as "Manifest Destiny" in the nineteenth century.