O'Neill was born on October 16,1888, in New York City, the son of a successful touring actor. His early life was spent on the road, a difficult life for a child. He later criticized the family's constant travelling, suggesting that the stress led to his mother's addiction to drugs as well as heavy drinking by the other family members. O'Neill started his college education at Princeton University, but that came to an abrupt end when he was dismissed for a prank. He married Kathleen Jenkins in 1909, producing a son, but divorced her only three years later. He then spent two years working as a sailor and manual laborer m South American ports.

In 1912 O'Neill was diagnosed with tuberculosis and sent to a sanitarium. Forbidden any strenuous physical activity, he resolved to get serious about his writing. During his recuperation, he became interested in playwrights, in particular the...