During the Civil War, President Abraham Lincoln freed the slaves with issuing the Emancipation Proclamation.  After the Civil War the 13th Amendment was ratified to free the slaves.  The 14th Amendment gave them citizenship and the 15th Amendment gave them the right to vote.  In the south, most of these amendments were ignored and blacks were not treated fairly.  Blacks did not fight for their rights again until the Civil Rights movements of the 1960s .

(http://www.history.com/topics/black-history/slavery).

Reconstruction after the Civil War