During the presidential campaign of 1844, John Louis O'Sullivan and Samuel J. Tilden founded and edited the New York Morning News
, a paper boosting the campaign of James K. Polk….In editorials in the News
and the [United States Magazine and] Democratic Review
, O'Sullivan outlined his vision of continental expansion summarized in the phrase "manifest destiny." O'Sullivan's expansionism was essentially peaceful, and his first editorials in the News
on the Mexican War questioned the circumstances of its initiation. By June 1846, because of investor dissatisfaction with his management style, O'Sullivan was ousted as editor of the News
and shortly thereafter disposed of his interest in the Democratic Review
…For the next few years, he pursued a number of enterprises, including two attempted invasions of Cuba in association with General Narcisco Lopez. A New York City jury acquitted him in March 1852 after he was indicted and tried for violating the Neutrality Act. Still affiliated with the Martin Van Buren wing of the New York Democracy, O'Sullivan represented that faction in patronage negotiations with president-elect Franklin Pierce. In 1854 he was appointed U.S. consul to Portugal and served until removed by President James Buchanan in 1858.
After his finances were depleted by his filibustering and failed business enterprises, O'Sullivan spent much of his final years in economic struggle. Living in Europe during the Civil War, he served the Confederacy as a propagandist and negotiator. Returning to the United States in the early 1870s, he promoted Spiritualism.