The Intercollegiate Socialist Society—prototype of the modern American student movement and the ancestor of Students for a Democratic Society (SDS)—was the first nationally organized student group that had a distinct political and ideological orientation. Its social and economic concerns, among them the labor and women’s suffrage movements, encompassed most of the issues agitating a rapidly changing society during the first two decades of this century. The ISS started a tradition of student political awareness and protest that has persisted to our day. For more than 15 years, it provided a forum for a group of gifted young men and women who, then and later, exercised influence far out of proportion to their numbers. This first full-scale study of the ISS follows the society from its birth in 1905 to its decline during World War I and the postwar period. Relying largely on original sources, Horn examines the structure, ideology, program, and tactics of the ISS and assesses its impact on students, faculty, and college administrators.