The Oscar-nominated film Lincoln starring Daniel Day-Lewis and Sally Field details the political maneuvering behind the passage of the 13th Amendment to the Constitution abolishing slavery. But a century and a half after President Abraham Lincoln’s death, the fight to end slavery has lingered on.

In 1865, the 13th Amendment was ratified, but not all states made it official; Mississippi got around to ratifying it on Feb. 7 of this year–148 years later–thanks to the help of two concerned men who saw the Steven Spielberg movie.

After watching the film, Dr. Ranjan Batra of the University of Mississippi became inspired to do some research and discovered online that after the Civil War, four states rejected the 13th Amendment, including his home state. Dr. Batra teamed up with his colleague, Ken Sullivan, and the team both helped the state correct this chapter in history.

Dr. Batra explained on The Last Word with Lawrence O’Donnell that his role was to find the right person to do the work. “[Ken] had the connections and his father knew someone who had actually written the bill for ratification in Mississippi and he knew exactly where to find it. All Ken had to do was pick up the copy of the bill.”

They brought the error to the attention of Mississippi’s current secretary of state, Delbert Hoseman, who agreed to send the resolution to the federal government.

In his research, Ken Sullivan, also of the University of Mississippi, found that the resolution was passed in a block vote. He continued, “There were several resolutions that were blocked together that was read in whole and the Senate just did a voice vote and that block of resolutions passed. So in that block of resolutions, it could have just got shuffled to the bottom and never found. It could have understood that it was completed, that the legislature had voted on it.”

Mississippi originally rejected the ratification of the 13th Amendment along with New Jersey, Delaware, and Kentucky. But, the other states symbolically ratified it years later. As it turns out, Mississippi, the final hold out state, voted to ratify the 13th Amendment in 1995, but Mississippi’s former secretary of state failed to send a copy of the resolution to the federal registrar to make the vote official.

The 13th 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.”