Al Capone owned Chicago in the roaring 1920s. On Wednesday we’ll see who owns Capone.

Johnson’s papers—several boxes’ worth— were the property of Johnson’s son George “Gene” E.Q. Johnson Jr. For most of the last few years they were in the possession of Chicago author Jonathan Eig, who drew from the documents to write his recent history of the gangland chief’s rise and fall, Get Capone. As Eig completed his book, Gene Johnson became ill, and the family decided to do what they’d always intended to do—donate the papers to the Chicago History Museum. The museum issued a deed of gift to the Johnsons last December, three months before Johnson died in his Lakeside home.

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Doug Bicknese, NARA’s regional archives director, says the papers would complement the “more formal” federal case files from the Prohibition era that NARA already maintains at its Great Lakes regional office at 7358 S. Pulaski. “We don’t necessarily keep records for every single person the U.S. district attorney prosecutes, but this is exceptional,” Bicknese says. “We will probably want the entire thing—the deliberation that went into the case, the handwritten notes, the closing arguments, the wiretaps, the correspondence.”

Eig calls the Johnson papers a “treasure trove.” There are typed notes regarding testimony and legal arguments and notes jotted by hand during the trial. Hand-drawn maps locate suspected Chicago “booze joints.” A letter from the attorney general in Washington—writing after Johnson reached a plea bargain agreement with Capone but before it fell apart—excoriates him for allowing so much time to go by before sentencing. The attorney general predicts that when the light sentence is announced the public will be outraged.

Eig stored the papers in cardboard boxes from a liquor store. “The archivists were horrified,” he says. “I said ‘Should I put them in files?’ and they said ‘No, don’t touch them.’ They took lots of pictures. For all they knew, I could lose the stuff or spill coffee on it or sell it on eBay.”

Gene Johnson told Hoffman, “Whenever I see a Hollywood version of the story, I feel like taking off my shoe and throwing it through the TV.” He lent Hoffman the papers so he could write a book that would set the record straight about who really got Capone. Not Eliot Ness—the mere Prohibition agent—and his Untouchables, but Johnson, the prosecutor and strategist.

And how did Gene Johnson get the papers? There was no National Archives until 1934, and not all government offices preserved their records. When George E.Q. Johnson went into private practice in 1933—he practiced until his death in 1949—he would have brought his important papers with him. What papers would’ve mattered more than the history of his prosecution of Al Capone?