From Ohio History Central
In 1845, John L. O'Sullivan, a newspaper reporter in New York City, coined the phrase "manifest destiny." O'Sullivan claimed that it was the God-given destiny of the United States of America to spread over North America.
The concept of manifest destiny did not end with the American Civil War. Throughout the late nineteenth century and well into the recent history of the United States, many Americans continued to believe that it was their nation's duty to spread the American political and economic system around the world.