Correspondence, diaries, articles, essays, sermons, notes, financial papers, printed material, broadsides, ship's papers, maps, and other papers relating chiefly to Libby's life and work as a peace activist and executive secretary of the National Council for Prevention of War (1921-1970). Includes material pertaining to his years as pastor of the Union Congregational Church, Magnolia, Mass. (1905-1911), and as a faculty member at Phillips Exeter Academy, Exeter, N.H. (1912-1920), to his travels in East Asia, Europe, the Middle East, and the South, and to war relief service with the American Friends Service Committee (1918-1920). Topics include Bible study, birth control, child labor, military preparedness, pacifism, and prostitution. Also includes a diary kept by Libby's father Abial Libby as a surgeon with Union forces during the Peninsular Campaign in Virginia in 1862. Correspondents include Markham W. Stackpole, pacifists Harold Studley Gray and Leyton Richards, and members of the Libby family.