Much of the scholarship dedicated to the working-class culture of early twentieth-century Wales concerns secular, economic, and political matters. Relatively little attention has been given to religion, despite the fact that the 1904-5 revival brought many thousands into contact with the chapel. This study examines the relationship between the labor movement and the nonconformist chapels, tracing the emergence of a "social gospel," its main protagonists, and its eclipse by the outbreak of World War II.