While feminist theories have surfaced from time to time in history, the modern feminist movement's roots are in the Age of Enlightenment with its principles of individual justice. In the United States, these ideas were put into action by Elizabeth Cady Stanton and others who issued a Declaration for Women's Independence in 1848. A central demand of their nascent feminist movement, women's right to vote, was achieved in 1920 after a 72-year battle.