In January 1915, suffragist Carrie Chapman Catt and settlement founder Jane Addams formed the Woman's Peace Party (WPP) to oppose World War I. The WPP advocated continuous mediation to end the war, as well as women's suffrage. Addams became WPP chair. By 1916, the WPP had two hundred branches and forty thousand members. Along with other peace groups, the WPP unsuccessfully urged President Woodrow Wilson to support mediation. Although the WPP had a national office and officers, local groups undertook much work on their own. When Wilson entered the war in 1917 and Congress passed laws suppressing dissent, divisions arose within the WPP, and many local groups disbanded. The national office and the Massachusetts branch supported war relief efforts, while the New York WPP strenuously opposed any war involvement. In 1919, after the war's end, women from Europe and the United States met in Zurich and created the Women's International League for Peace and Freedom (WILPF). The Woman's Peace Party then became the US Section of WILPF.

This collection includes files from 1914 to 1920, more than half of which consist of WPP correspondence. The remaining materials are administrative and historical records from the national office and several state branches of the organization. These include board meeting minutes, speeches, membership lists, resolutions, financial information, Congressional hearing reports, committee reports, form letters, press releases, study course and reference materials, clippings, pictures, and periodicals.

National office correspondence illustrates the WPP's coordination with other peace groups and its work across the United States, including opposition to school physical education classes emphasizing military training; involvement in the Ford peace expedition; work with conscientious objectors; and involvement in food relief after the United States entered the war. State-level materials include records of the Massachusetts branch's conferences and study courses and the New York group's periodical, Four Lights. Documentation from other local branches highlights legislative and civic actions. Well-known correspondents include Jane Addams, Emily Greene Balch, Crystal Eastman, and Woodrow Wilson.

The collection is vital for those researching the twentieth-century peace movement, women's studies, suffrage, and American history in general at the end of the Progressive Era.