Twenty Irish immigrants, suspected of belonging to a secret terrorist organization called the Molly Maguires, were executed in Pennsylvania in the 1870s for the murder of sixteen men. Ever since, there has been enormous disagreement over who the Molly Maguires were, what they did, and why they did it, as virtually everything we now know about the Molly Maguires is based on the hostile descriptions of their contemporaries. Arguing that such...