The Thirteenth Amendment to the United States Constitution, passed by the Senate on April 8, 1864, by the House on January 31, 1865, and ratified on December 6, 1865, abolished slavery as a legal institution.
The Constitution, although never mentioning slavery by name, refers to slaves as "such persons" in Article I, Section 9 and “a person held to service or labor” in Article IV, Section 2. The Thirteenth Amendment, in direct terminology, put an end to this. The amendment states:
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."
The history behind this amendments adoption is an interesting one. Prior to the Civil War, in February 1861, Congress had passed a Thirteenth Amendment for an entirely different purpose--to guarantee the legality and perpetuity of slavery in the slave states, rather than to end it. This amendment guaranteeing slavery was a result of the complicated sectional politics of the antebellum period, and a futile effort to preclude Civil War. Although the Thirteenth Amendment that guaranteed slavery was narrowly passed by both houses, the Civil War started before it could be sent to the states for ratification.
But the final version of the Thirteenth Amendment--the one ending slavery--has an interesting story of its own. Passed during the Civil War years, when southern congressional representatives were not present for debate, one would think today that it must have easily passed both the House of Representatives and the Senate. Not true. As a matter of fact, although passed in April 1864 by the Senate, with a vote of 38 to 6, the required two-thirds majority was defeated in the House of Representatives by a vote of 93 to 65. Abolishing slavery was almost exclusively a Republican party effort--only four Democrats voted for it.
It was then that President Abraham Lincoln took an active role in pushing it through congress. He insisted that the passage of the Thirteenth Amendment be added to the Republican party platform for the upcoming presidential elections. He used all of his political skill and influence to convince additional democrats to support the amendments' passage. His efforts finally met with success, when the House passed the bill in January 1865 with a vote of 119-56. Finally, Lincoln supported those congressmen that insisted southern state legislatures must adopt the Thirteenth Amendment before their states would be allowed to return with full rights to Congress.
The fact that Lincoln had difficulty in gaining passage of the amendment towards the closing months of the war and after his Emancipation Proclamation had been in effect 12 full months, is illustrative. There was still a reasonably large body of the northern people, or at least their elected representatives, that were either indifferent towards, or directly opposed to, freeing the slaves.
The Effect of the Emancipation Proclamation
Modern historians occasionally criticize Lincoln's Emancipation Proclamation, declaring it a hollow document that "freed no slaves." Signed by President Lincoln on January 1, 1863, it proclaimed that “all persons held as slaves within any State, or designated part of a State, the people whereof shall then be in rebellion against the United States, shall be then, thenceforward, and forever free.”
Lincoln correctly realized that as President, he had no legal grounds to single-handedly terminate the institution of slavery--but that this had to be done by a constitutional amendment. The Emancipation Proclamation was simply a war powers action by he, the commander in chief of the armies, in which he attempted to remove all the slaves from the southern peoples "in rebellion against the United States.” Even in this, Lincoln was very anxious about the legality of his actions. He worded the document very carefully, in legal terms, in his attempt to make it legally binding in future courts of law.
He recognized that the Emancipation Proclamation would have to be followed quickly by a constitutional amendment in order to guarantee the abolishment of slavery.
Although the Emancipation Proclamation had no theoretical effect on the legal status of slaves in the border states, or slaves in regions of the country not currently under the control of southern armies, it had, in fact, a great deal of practical impact on the legality of slavery everywhere--North and South. As northern armies marched through the south, which General Sherman and his army soon began doing, thousands of slaves followed in their wake--and were never again under the legal authority of their former masters. So the argument that the Emancipation "freed no slaves" is a specious one. Until the Thirteenth Amendment was was fully ratified by the necessary majority of the states in December of 1865, the Emancipation Proclamation was the document used to justify separating slaves from their masters, and by late 1865 there were no slaves remaining in the United States. Consequently, the Emancipation Proclamation was truly the beginning of the end of slavery.
The Original Thirteenth Amendment
Long before the Civil War, a Thirteenth Amendment had been proposed for an unrelated purpose--see the following site for this story:
The Original Thirteenth Amendment: Titles of Nobility and Honour, An Essay