Where did the term manifest destiny come from?

The term "manifest destiny" originated in the United States in the 1840s, encapsulating the belief that American expansion across the continent was both justified and inevitable. It was popularized by journalist John L. O'Sullivan, who used the phrase in 1845 to advocate for the annexation of Texas. The concept reflected a sense of mission and entitlement, suggesting that it was America's destiny to spread democracy and civilization westward. This ideology played a significant role in the westward expansion and the policies of the U.S. government during that era.