Nineteenth Amendment
The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of sex.
Congress shall have power to enforce this article by appropriate legislation.
This amendment was ratified in 1920, as advocates ("suffragettes") cited women's support of World War I to persuade President Woodrow Wilson to change his position from opposing this amendment to supporting it. Women could already vote in many areas of the country, but this amendment guaranteed the right, in violation of the principle of states' rights and in support of individual civil rights, a phenomenon further seen in civil rights legislation after the civil rights movement. 'States rights' is conservative code for being able to oppress minorities. For example in the civil rights campaign many southern white racists claimed that they were simply seeking 'State Rights' to self determination when really they were just attempting to maintain racist laws but to admit this would have been difficult.