Originally intended to be part of a nine-play cycle entitled A Tale of Possessors Self-Dispossessed, Mansions was an incomplete rough draft written between 1936 and 1939 that O'Neill did not want posthumously finished or produced.
A sequel to A Touch of the Poet, it picks up four years later in 1832 Massachusetts, with Simon Harford, now married to Sara Melody, finding himself the pawn in a battle between his wife and his mother to control him through love.
The title of the play was derived from the line "Build thee more stately mansions, O my soul" in the poem The Chambered Nautilus by Oliver Wendell Holmes.
Against his wishes, O'Neill's widow, Carlotta Monterey, authorized Karl Ragnar Gierow of the Swedish Royal Dramatic Theatre to turn the unfinished work into an acting version.
The play was the inaugural production at the Ahmanson Theatre in Los Angeles, where it opened on April 12, 1967 with Ingrid Bergman, Colleen Dewhurst, and Arthur Hill in the leading roles.