Charles C. Wilson is credited in studio records for the role of "Welch", but that role was played by Willard Robertson. Also, Harry Tyler in the role of "Johnny" was not seen in the print.
Michael A. Musmanno's story, "Jan Volkanik", may have been unpublished when this film was released, but it was published as a novel in 1966 with the title "Black Fury". Harry R. Irving's play, "Bohunk" was unproduced and possibly unpublished.
Mike's murder was based on an actual strike case in which a miner was killed by three company policemen.
The film was banned outright in Chicago, Guatemala, Spain, Peru, Venezuela, Trinidad and other countries. Many other locales required cuts in police brutality, Mike's murder and the mine explosions. The Hays office was concerned about Joe's criminal behavior in setting off the mine explosions not being punished, but eventually issued a certificate of approval.