Answer: 2013
Congress voted for the 13th Amendment in January 1864, and it then went on to states for ratification. Back then, Delaware, Kentucky, New Jersey and Mississippi rejected the measure,
according to the Hattiesburg American, and in the months and years that followed, those states too ratified the amendment.
Mississippi, however, had an asterisk next to its name -- the state ratified the amendment in 1995, according to the news outlet, but "because the state never officially notified the U.S. Archivist, the ratification is not official.”
It wasn't until the movie Lincoln hit the theaters that this discovery was made -- after Dr. Ranjan Batra, associate professor of neurobiology and anatomical sciences at the University of Mississippi Medical Center, saw the film in November 2012, he wondered what happened when the states voted on ratification.
The state rectified the situation by officially ratifying the 13th Amendment on Feb. 7, 2013.
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It should be noted that the Emancipation Proclamation and the 13th Amendment are not the same thing. The 13th Amendment abolished slavery nationwide, the Emancipation Proclamation was a wartime order and freed slaves in rebellious states.