On December 6, 1865, the Thirteenth Amendment became part of the United States Constitution.
Note that when the amendment went out to the state legislatures for ratification, Abraham Lincoln affixed his signature … an unnecessary part of the process. Just ask Andrew Johnson.
That’s how the New York Herald informed its readers of this event on December 7. Note that it was Georgia’s ratification that made the amendment part of the Constitution.
Free at last, indeed. What freedom would mean was still left to be defined.