And believe it or not, it's all thanks to the movie 'Lincoln'.

Library of Congress

Related Film 'Lincoln' Inspires Look into Slavery Vote Clarion Ledger

Here’s an outcome the producers of the movie Lincoln probably never expected: it indirectly led to the official ratification of the 13th amendment to ban slavery in Mississippi, nearly 150 years after its adoption.

The story began in November last year, when Ranjan Batra, an associate professor at the University of Mississippi Medical Center, went to see director Steven Spielberg’s Oscar-nominated historical drama Lincoln, reports the Jackson, Miss. Clarion-Ledger. Spielberg’s civics lesson tells the story of the final months of President Abraham Lincoln’s life and his efforts to get the 13th amendment to the U.S. Constitution passed by the House of Representatives.

(PHOTOS: The Men Behind Lincoln: Daniel Day-Lewis and Steven Spielberg by Marco Grob )

After watching the film, Batra was curious to find out what happened to the amendment once it was passed. It went on to be adopted in less than a year when 27 of the then 36 states ratified it by the end of 1865. Mississippi was the last of these states to do so — they finally got around to it in 1995 — but Batra spotted a curious detail next to the state’s name on thewebsite usconstitution.net: the ratification was unofficial, as Mississippi never formally notified the U.S. archivist.

Batra mentioned the oversight to a friend, Ken Sullivan, who recalled the 1995 debate over the law and tracked down a copy of the resolution. It had been passedby the Mississippi Senate and House — unanimously, recalled the bill’s introcuder, Sen. Hillman Frazier to the Clarion-Ledger — but inexplicably had never beensent to the Office of the Federal Register.

(MORE: Should States Apologize for Slavery?)

Once the paperwork was eventually filed, the state received notification on Feb. 7 from the director of the Federal Register that it had officially ratified the 13th Amendment — 148 years late. “We finally got it right,” Frazier said to the newspaper.