John L. O'Sullivan
John Louis O'Sullivan (November 15, 1813 – March 24, 1895) was an American columnist and editor who used the term "Manifest Destiny" in 1845 to promote the annexation of Texas and the Oregon Country to the United States. O'Sullivan was an influential political writer and advocate for the Democratic Party at that time and served as US Minister to Portugal during the administration of President Franklin Pierce (1853–1857), but he largely faded from prominence soon thereafter. He was rescued from obscurity in the twentieth century after the famous phrase "Manifest Destiny" was traced back to him.
Read more about John L. O'Sullivan: "Manifest Destiny", Later Years