In the days before the start of the civil war several amendments were proposed in effort to bring the union back together. One was 
Joint House Resolution 80, otherwise known as the Corwin Amendment. The original text is as follows:
H_Res 80
Joint Resolution to amend the Constitution of the United States
Resolved by the Senate and House of Representatives of the United States of America in Congress assembled. State the following article be proposed to the Legislatures of the several(?) states as an amendment to the Constitution of the United States, which, when ratified by three-fourths of said Legislatures shall be valid, to all intent and purposes as part of said Constitution, (?)
Article XIII. No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any state, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State.
Passed the house of Representatives
February 28th, 1861
Senate of the United States
March 3, 1861
Resolved (two-thirds of the senate present concurring therein) that this Joint Resolution do pass.
In fact, not only was it not presented by southern states, it was not voted on by them, nor ratified by them. It was ratified by three northern states. It was not voted on by southern states as they had already seceded from the union. It, in fact, was introduced to the senate by Senator William H Stewart of New York, and into the house by Representative Thomas Corwin of Ohio. And it was only one of many such amendments proposed. It passed the house with a vote of 133 to 65 on Feb. 28, 1861. On March 2, 1861 it passed the senate with no changes with a vote of 24 to 12. As previously stated, the senators and representatives from the 7 southern states that already seceded did not vote; it still passed both the senate and house by the needed two-thirds majority votes.
Out-going President James Buchanan, a Democrat, endorsed the Corwin Amendment by taking the unprecedented step of signing it.[16] His signature on the Congressional joint resolution was unnecessary, as the Supreme Court, in Hollingsworth v. Virginia (1798), ruled that the President has no formal role in the constitutional amendment process.
Abraham Lincoln, in his first inaugural address, said of the Corwin Amendment:
I understand a proposed amendment to the Constitution—which amendment, however, I have not seen—has passed Congress, to the effect that the Federal Government shall never interfere with the domestic institutions of the States, including that of persons held to service....holding such a provision to now be implied constitutional law, I have no objection to its being made express and irrevocable.
The only thing needed for this to become an actual amendment would be the three-fourths of states ratification. Three union states ratified it: Ohio, Maryland, and Illinois. If the seven southern states had wished, they could have come back and ratified it as well. It would have protected slavery, and as written, would not be able to be rescinded. That would have given 10 states out of the 36 to have passed it. It would have needed only seventeen more states to ratify it. And since the Civil war was about slavery, and 11 states eventually seceded, the other four surely would have also ratified, right? That would have left only thirteen. Lincoln, in desperate attempts to reconcile the union, stated if he could make slavery legal to save the union, he would do it. Surely, he could have influenced other states to ratify it, couldn't he? But a president ever do that?
Just weeks prior to the outbreak of the Civil War, Lincoln sent a letter to each state's governor transmitting the proposed amendment, noting that Buchanan had approved it.
The Corwin Amendment was the second proposed "Thirteenth Amendment" submitted to the states by Congress. The first was the similarly ill-fated Titles of Nobility Amendment in 1810.
