The Brotherhood of the Kingdom was an American Protestant society, formed by Walter Rauschenbusch and Leighton Williams, with the purpose of championing Social Gospel theories. 
- ↑ Gould, S. C., ed. (April 1905), Altrurian Order of Mystics, "Arcane Societies in the United States", Historic Magazine and Notes and Queries 23 (4): 86, https://babel.hathitrust.org/cgi/pt?id=njp.32101064475955;view=1up;seq=104, retrieved 2016-04-28, "An interdenominational society of men and women, "who believe in the Kingdom of God on Earth, and who have united to establish the idea in the thought of the church and to assist in its practical realization in the world." Comprehension of its aims, Harmony of its spirit, and Cooperation with its desires are the three cardinal qualifications for membership. Walter Rauschenbusch is corresponding secretary, 407 W. 43rd Street, New York City."