A Mississippi professor's historical research, inspired by the movie "Lincoln," led to his state's belated ratifying of the 13th Amendment, nearly 150 years after its initial passing.

The Jackson Clarion-Ledger reported on Sunday that the state had passed a resolution ratifying the amendment, which mandated the abolition of slavery, in 1995. But somehow, that resolution was never sent to the Office of the Federal Register until last month, when current Secretary of State Delbert Hosemann sent a copy to the Office of the Federal Register.

The clerical error came to light following a search late last year by Ranjan Batra, an associate professor of neurobiology at the University of Mississippi Medical Center, who looked up various state votes on the amendment after watching "Lincoln." Batra discovered that the state had "an asterisk" behind it indicating the ratification was never made official.

He then informed a colleague, Ken Sullivan, who contacted the Federal Register to confirm the mistake; when the state ratified the amendment in 1995, then-Secretary of State Dick Molpus' office was supposed to have sent a copy.

"What an amendment to have an error in filing," Molpus told the newspaper. "Thanks to Ken Sullivan for being a good citizen in bringing this oversight to light, so it can be corrected."

There has been no explanation as to why Molpus' office never sent the original copy to federal officials for ratification.

[Image via Shutterstock]