Sean O'Casey was born John Casey on March 30, 1880 in Dublin, Ireland, to Michael and Susan (Archer) Casey, a lower-middle class Protestant family. His father died in 1886. As a child, O'Casey suffered from trachoma, which affected his sight and made it difficult for him to succeed scholastically. He worked periodically throughout his adolescence as a stock boy, a van driver, and railway laborer. During this time, he became interested in Irish working class culture, as well as socialism and labor causes. In 1906 he joined the Gaelic League and began learning the Irish language. He changed his name to Sean O'Cathasaigh and began writing, primarily poetry. A few years later he joined the Irish Transport and General Workers Union and its offshoot, the Irish Citizen Army. He took part in the Dublin lock-out strike in 1913; however, he resigned from these organizations in 1914 and criticized their roles in the Easter Rising of 1916.

O'Casey began writing plays around 1916. His first play to be performed was The Shadow of a Gunman, produced in 1923 by the Abbey Theatre. By this time he had assumed the final iteration of his name, Sean O'Casey. He found continued success (and controversy) with subsequent plays, Juno and the Paycock and The Plough and the Stars. In 1926, he met Eileen Carey, an actress who was performing in the West End production of The Plough and the Stars, and they married on September 23, 1927. Together they had three children, Breon, Niall, and Shivaun.

Due to an increasingly strained relationship with the Abbey Theatre, which refused to produce his play The Silver Tassie, O'Casey and his new family moved permanently to England in 1929. He continued to write, and during this time produced plays, including Within the Gates (1934), The Star Turns Red (1940), and Purple Dust (1943). He also gained a following across the Atlantic when Lillian Gish starred in a production of Within the Gates in New York City.

Towards the end of his life O'Casey contended with increasing blindness. His son, Niall, died from leukemia in 1956. O'Casey died of a heart attack on September 18, 1964, at the age of 84.

Sources:

Cave, Richard Allen. "O'Casey, Sean (1880-1964), playwright and writer." In Oxford Dictionary of National Biography, Oxford University Press (2004), accessed November 3, 2016, http://www.oxforddnb.com/view/article/35283.

Donoghue, Dennis. "The advantage he lacked was poverty." In The New York Times Book Review, July 3, 1988, http://www.nytimes.com/1988/07/03/books/the-advantage-he-lacked-was-poverty.html

Moran, James. "Sean O'Casey." In Oxford Bibliographies in British and Irish Literature, accessed November 3, 2016, http://www.oxfordbibliographies.com.proxy.bc.edu/view/document/obo-9780199846719/obo-9780199846719-0101.xml