The 13th Amendment to the US Constitution was ratified on December 18, 1865 during Reconstruction. Along with the 14th amendment and the 15th amendment, it is one of the three Reconstruction amendments.
Text of the 13th Amendment
Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Congress shall have power to enforce this article by appropriate legislation.