The answer is "The Molly Maguires were a group of union organizers who were prosecuted and either executed or imprisoned after an 1875 strike against anthracite mine owners failed."
They originated as a secret society in Ireland, and they were active in Liverpool, in Ireland and in certain parts of the USA like Pennsylvania. In the beginning, in Ireland they were considered a rural and Gaelic association. The Irish immigrants brought the Molly Maguires and similar associations to America with them as a clandestine society. After the violent protests, the Molly Maguires were arrested by the Coal and Iron Police, charged with murder, arson and kidnapping among other crimes and they were hangued.
