Manton Marble was born in 1834 in Worcester, Massachusetts, but attended school in Albany, New York, where his family had moved in 1840. He continued his studies at Rochester University, working as an apprentice for the Rochester American newspaper. After graduating in 1855, he edited two Boston newspapers, and then took an editorial position with the New York Evening Post in 1858. Two years later, he took a job as night editor for the New York World, which had just begun publication, and became its chief editor in 1862. Financed by wealthy New York Democrats, such as August Belmont and Samuel Tilden, Marble made the daily newspaper into the chief organ of the Democratic Party in New York City. 

The World backed the Union military cause during the Civil War, but criticized Lincoln administration policies, especially emancipation, government centralization, and violations of civil liberties. It became a victim itself of press censorship when the military briefly suspended its publication for printing an article on the alleged defeatist attitude of the Lincoln White House. During the 1864 presidential campaign the World endorsed George McClellan, the Democratic nominee, and stood against racial equality by playing on white fears of miscegenation.

After the Civil War, Marble opposed the Reconstruction policies of the radical Republicans, but after heavy Democratic losses in the 1866 elections, he advised fellow partisans to accept voting rights for black men as an accomplished fact. In the 1868 race for the Democratic presidential nomination, he supported Salmon Chase, an advocate of black voting rights and of amnesty for former Confederates. Chase lost to Horatio Seymour, who was soundly defeated by General Ulysses S. Grant, the Union war hero, in the general election. In the 1872 election, Marble joined other Democrats to endorse the candidacy of Liberal Republican Horace Greeley. Thereafter, Marble became a leading promoter of Samuel Tilden, who was elected governor of New York in 1874 and narrowly lost the disputed presidential election of 1876 to Republican Rutherford B. Hayes. Allegations that Marble attempted to bribe a Florida elector were never proved. 

Marble established the World as a major force in American journalism and in 1866 beat out both the New York Herald and the Associated Press for control of news transmitted by the transatlantic telegraph cable. By 1868, he personally had controlling interest in the journal and was able to become independent of Democratic Party oversight, although he continued to support Democratic policies and candidates. Readership declined, however, and the paper suffered heavy financial losses during the depression of the early 1870s. In 1876, Marble sold the World to Thomas A. Scott, president of the Pennsylvania Railroad.