What did the 13th amendment establish?

The thirteenth amendment to the U.S. Constitution reads as follows:

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 thirteenth amendment, therefore, establishes that slavery is illegal in all states and territories of the United States.
The legislation amending the Constitution to outlaw slavery was passed and ratified in early 1865. Its passage was a top legislative priority of President Lincoln after his reelection in 1864. He wanted to ensure the Emancipation Proclamation freeing the slaves could not be overturned.
Interestingly, however, slavery or involuntary servitude is allowed as punishment for a crime in this country, which is why people in prison can be set to work at very low or no wages.
This was a landmark amendment, finally settling the divisive question of slavery in the United States. Never again would there be free states and slave states. Issues of racism persist up until the present day, but the important principle of human freedom has never again been seriously questioned.