O’Neill was an almost immediate success once he embarked upon his playwriting career. He wrote his first one-act play, Bound East for Cardiff, in 1914 and had it produced by the Provincetown Players in 1916. His first full-length play, Beyond the Horizon (pr. 1920), was produced on Broadway, ran for 111 performances, and was awarded the Pulitzer Prize. This combination of popular and critical success continued through a string of increasingly ambitious and experimental plays, among them such triumphs as The Emperor Jones (pr. 1920); Anna Christie (pr. 1921), which won for O’Neill his second Pulitzer; The Hairy Ape (pr. 1922); All God’s Chillun Got Wings (pr., pb. 1924); Desire Under the Elms (pr. 1924); The Great God Brown (pr., pb. 1926); Strange Interlude (pr., pb. 1928), which was awarded yet a third Pulitzer Prize; Mourning Becomes Electra (pr., pb. 1931), a trilogy of three plays; and Ah, Wilderness! (pr., pb. 1933), an uncharacteristic comedy. All of these were critically acclaimed, and all ran for more than a hundred performances.

After the Theatre Guild (the company with which he had come to be permanently associated) produced Days Without End (pr., pb. 1934), O’Neill apparently went into retirement. His power as a dramatist appeared to have ebbed, and the play was, by O’Neill’s standards, somewhat of a failure with the public and critics. He had long been considered the greatest of American playwrights, and the award of the Nobel Prize in 1936 might have provided the fitting end to a great career. In fact, however, his best work was still to come.

When O’Neill completed The Iceman Cometh in 1939, he considered it among his finest plays. When it was finally produced in 1946, the critics generally agreed that it was a brilliant and powerful, if somewhat flawed and erratic, work, but it was the 1956 production at The Circle in the Square Theatre in New York, directed by Jose Quintero, that ran for an amazing 565 performances and secured the play its status as one of the few unquestionable masterpieces of the American theater. Today The Iceman Cometh, together with O’Neill’s posthumously produced Long Day’s Journey Into Night (pr., pb. 1956), is generally considered the most important work in American dramatic literature.