While the Thirteenth Amendment outlawed slavery, the original proposed Thirteenth Amendment was altogether different. Approved by Congress in 1810, the Titles of Nobility Amendment was designed to strip U.S. citizenship from any citizen who accepted an aristocratic title from a foreign country. Ratified by twelve states (the last in 1812) the proposed amendment is technically still pending but would require ratification by an additional twenty-six states. It was erroneously included as the Thirteenth Amendment in some early-nineteenth-century Constitutional publications despite never having been ratified. ‘Thirteenthers’ is a term sometimes used to refer to people who maintain it was in fact ratified, or those who support its ratification now. An interesting article from 2010 on attempts to ‘restore’ this proposed amendment in Iowa may be found here.