On the outbreak of the First World War a group of women pacifists in the United States began talking about the need to form an organization to help bring it to an end. On the 10th January, 1915, over 3,000 women attended a meeting in the ballroom of the New Willard Hotel in Washington and formed the Woman's Peace Party. Jane Addams was elected chairman and other women involved in the organization included Mary McDowell, Florence Kelley, Alice Hamilton, Anna Howard Shaw, Belle La Follette, Fanny Garrison Villard, Emily Balch, Jeanette Rankin, Lillian Wald, Edith Abbott, Grace Abbott, Crystal Eastman, Carrie Chapman Catt, Emily Bach, and Sophonisba Breckinridge.

In April 1915, Arletta Jacobs, a suffragist in Holland, invited members of the Woman's Peace Party to an International Congress of Women in the Hague. Jane Addams was asked to chair the meeting and others who attended from the United States included Alice Hamilton, Grace Abbott and Emily Bach. Others who attended included Lida Gustava Heymann (Germany); Emmeline Pethick-Lawrence, Emily Hobhouse, (England); Chrystal Macmillan (Scotland) and Rosika Schwimmer (Hungary). Afterwards, Jacobs, Addams, Macmillan, Schwimmer and Balch went to London, Berlin, Vienna, Budapest, Rome, Berne and Paris to speak with members of the various governments in Europe.

It was decided to form the Women's International League for Peace and Freedom (WILPF). Emily Bach, who was dismissed as professor of political economy at Wellesley College as a result of her anti-war activities, became secretary of the organization.

The WILPF continued after the war and the international headquarters of the organization is based in Geneva. and there are branches in around 50 different countries.