The leader of the American temperance movement was Frances Willard. She served as the president of the Women's Christian Temperance Union (WCTU) and became a prominent figure in advocating for the prohibition of alcohol in the late 19th and early 20th centuries. Willard's efforts extended beyond temperance; she strongly supported women's suffrage and social reforms, arguing that alcohol was a systemic cause of social problems. Her leadership helped to mobilize a massive grassroots movement that influenced public opinion and political policy, ultimately contributing to the passage of the 18th Amendment, which instituted Prohibition in the United States in 1920.