Molly Maguires
One of the best known undercover agents was James McParland who, under the alias of James McKenna, infiltrated a secret society of Pennsylvania coalminers called the Molly Maguires. Debate continues over the extent of guilt on the part of the Mollies, and over the question of whether they were in some sense a labor organization, or merely a ring of assassins lashing out over unjust working conditions, inadequate pay, and the pressures of persecution against their Irish Catholic status. In any event, McParland's testimony resulted in nineteen of the Molly Maguires going to the gallows.