As a writer, Yeats is part of the Celtic Revival movement that occurred in the late 19th century. Designed to acknowledge and incorporate Celtic mythology, history, and iconography into literature, arts, and crafts, the Celtic Revival was important in Wales, Scotland, and England. However, it is particularly associated with the Irish Literary Revival. As writers of poetry and drama, Yeats, Lady Gregory, J. M. Synge, Sean O’Casey, Edward Martyn, and Lord Dunsany all participated in work that assessed the past, current, and future state of Ireland. Yeats wrote many popular poems about Irish history and Celtic folklore. In his book of essays, The Celtic Twilight (1893), Yeats argued that the death of Charles Stewart Parnell in 1891 created a gap in the focus on Irish nationalism which must be closed by accomplishments in the arts. To support other Irish writers in this endeavor, Yeats helped to establish the Irish Literary Society in London in 1892, the National Literary Society in Dublin in 1892, and the Irish National Theatre (with Lady Gregory and Robert Martyn) in 1899, which later transformed into the National Theatre Society at the Abbey Theatre in 1904. “The Lake Isle of Innisfree” uses several references to Ireland and Irish lore.