1845: Journalist John L. O'Sullivan argues for "manifest destiny"

American Progress, (1872) by John Gast

(Wikipedia) ... O'Sullivan's second use of the phrase became extremely influential. On December 27, 1845, in his newspaper the New York Morning News, O'Sullivan addressed the ongoing boundary dispute with Britain. O'Sullivan argued that the United States had the right to claim "the whole of Oregon":
And that claim is by the right of our manifest destiny to overspread and to possess the whole of the continent which Providence has given us for the development of the great experiment of liberty and federated self-government entrusted to us.

That is, O'Sullivan believed that Providence had given the United States a mission to spread republican democracy ("the great experiment of liberty"). Because Britain would not spread democracy, thought O'Sullivan, British claims to the territory should be overruled. O'Sullivan believed that manifest destiny was a moral ideal (a "higher law") that superseded other considerations. Continued