The chapter introduces the origins of the plebiscite as a tool of international politics, and examines Sarah Wambaugh’s early career in the American women’s peace and suffrage movements. Wambaugh began researching the plebiscite following American entry into the First World War in 1917, and her early contributions reflected her youthful idealism and embrace of the principle of the self-determination of nations pronounced by Woodrow Wilson. Her early works may have influenced the peacemakers during the Paris Peace Conference of 1919; however, the plebiscites that resulted were more frequently the result of instrumental bargaining among the victorious powers. If the plebiscite was not used as consistently as advocates such as Wambaugh would have liked, a major achievement was the inclusion of women’s suffrage in nearly all plebiscites written into the post-war settlement. In this the first plebiscite decided upon for the Danish–German border region of Schleswig set an important precedent.