Hate to break it to you but slavery did not end in the United States, it outlaws it's use except in the case of lawful detention. Ie. The state and the feds can own people but you nor I cannot.
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.
Section 2
Congress shall have power to enforce this article by appropriate legislation.