Rebecca Shelley was a pacifist and feminist. Born Margaret Rebecca Shelly, she occasionally used the spelling Shelley to shield her family and to honor the poet Percy Bysshe Shelley. She trained at Clarion Normal School and taught German in Wisconsin, Washington, and Illinois. Shelley became engaged to a German, Franz Willman, but he enlisted in the German army in World War I and died before the end. Shelley became a pacifist and joined Jane Addams as an American delegate to the International Council of Women. Shelley was a member of the Ford Peace Ship delegation and was involved with a number of peace organizations. Exhausted with the work, she settled in Michigan in 1918 to publish The Modern Poultry Breeder. She founded the Battle Creek chapter of the Women's International League for Peace and Freedom and helped organize World Peace Month in 1952. Into her nineties, Shelly continued her work for peace, protesting the Vietnam war.
She married German native Felix Martin Rathmer in 1922. Federal law mandated, at that time, that women who married foreigners lost their American citizenship. While this law was repealed just a month after her marriage, Shelley would not regain her citizenship until 1944, as she refused to take an oath of allegiance to the United States that included an agreement to bear arms.