The U.S Constitution defines citizenship in its Fourteenth Amendment, which was ratified on July 9th, 1868. The Amendment grants citizenship to every person who was born or has been naturalized in the United States. Due to the time when it was ratified, the Amendment helped to established that all African-American people that were now emancipated after the conclusion of the Civil War, were now considered citizens of The United States, and therefore were granted civil rights.
