Unlike the film narrative, in real life Dr. Mudd had been part of an earlier conspiracy to kidnap President Lincoln and exchange him for Confederate prisoners, which constitutes treason.

[1] A few hours after the assassination of President Abraham Lincoln (Frank McGlynn Sr.), Dr. Samuel Mudd (Warner Baxter) gives treatment to a man with a broken leg who shows up at his door.

Mudd is soon afterward arrested for being an accessory in the assassination, is convicted, and is then sent to Arcadia, a prison on the Dry Tortugas that is referred to in the film as "America's own Devil's Island".

"[2] Variety reported that "Warner Baxter [...] turns in a capital performance as the titular prisoner of ‘America’s Devil’s Island’", and described the casting as "tiptop", with "John Carradine stand[ing] out as a new face among especially sinister heavies.

"[3] Writing in Turner Classic Movies, critic Jeremy Arnold described the film as a "highly entertaining, fast-moving film with endlessly fascinating subject matter," being "one of director John Ford's less-talked-about pictures" and noting that "John Carradine [...] is deliciously evil and nasty in one of the most memorable performances of his career [and] Warner Baxter as Mudd gives perhaps THE best performance of his own career.