The US House passed Amendment XIII to the United States Constitution on January 31, 1865. The Thirteenth Amendment abolished slavery:

Amendment XIII

Section 1.
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.

The requisite number of states ratified Amendment XIII on December 6, 1865, and the US formally adopted it on December 18, 1865.

Douglas Wilson and Steve Wilkins wrote:

None need lament the passing of slavery. But who cannot but lament the damage to both white and black that has occurred as a consequence of the way it was abolished? We are forced to say that, in many ways, the remedy which has been applied has been far worse than the disease ever was. (Southern Slavery As It Was [Moscow, ID: Canon Press, 1996], 38; emphasis original)