The Third Great Awakening refers to a hypothetical historical period that was marked by religious activism in American history and spans the late 1850s to the early 20th century. It affected pietistic Protestant denominations and had a strong element of social activism. It gathered strength from the postmillennial belief that the Second Coming of Christ would occur after mankind had reformed the entire earth. It was affiliated with the Social Gospel Movement, which applied Christianity to social issues and gained its force from the Awakening, as did the worldwide missionary movement. New groupings emerged, such as the Holiness, Nazarene, and Christian Science movements.