Educated at boarding schools… attended Princeton University for one year … after left school to begin his real education in "life experience." He shipped to sea, lived a derelict's existence on the waterfronts, submerged himself in alcohol, and attempted suicide. … held a job for a few months as a reporter… came down with tuberculosis. Confined to a sanitarium he confronted himself soberly and nakedly for the first time and seized the chance for what he later called his "rebirth." He began to write plays.
O'Neill's first appearance as a playwright came in the summer of 1916, in Provincetown, Mass., where a group of young writers and painters had launched an experimental theatre. Between 1920 and 1943 he completed 20 long plays and a number of shorter ones. … deriving directly from the scarring effects of his family's tragic relationships. O'Neill's only comedy, Ah, Wilderness!, appeared on Broadway in 1933. Significantly, the play is set in the same place and period, a small New England town in the early 1900s, as his later tragic masterpiece, Long Day's Journey into Night.
O'Neill's tragic view of life was perpetuated in his relationships with the three women he married--two of whom he divorced--and with his three children. His elder son committed suicide… his younger son drifted into a life of emotional instability. His daughter Oona was cut out of his life when she married Charlie Chaplin. [The actress Geraldine Chaplin is their daughter.]

Although respected in the United States, was more highly regarded abroad. In 1936 the Swedish Academy gave O'Neill the Nobel Prize for Literature, the first time the award had been conferred on an American playwright.
O'Neill's final years were spent in grim frustration. Unable to work, he longed for his death and sat waiting for it in a Boston hotel, seeing no one except his doctor, a nurse, and his third wife, Carlotta Monterey. O'Neill died as broken and tragic a figure as any he had created for the stage.