Pinkertons),busting heads for the establishment since 1850.

During the labor strikes of the late 19th and early 20th centuries, businessmen hired the Pinkerton Agency to infiltrate unions, supply guards, keep strikers and suspected unionists out of factories, and recruit goon squads to intimidate workers. One such confrontation was the Homestead Strike of 1892, in which Pinkerton agents were called in to reinforce the strikebreaking measures of industrialist Henry Clay Frick, acting on behalf of Andrew Carnegie.[5] The ensuing battle between Pinkerton agents and striking workers led to the deaths of seven Pinkerton agents and nine steelworkers.[6] The Pinkertons were also used as guards in coal, iron, and lumber disputes in Illinois, Michigan, New York, Pennsylvania, and West Virginia as well as the Great Railroad Strike of 1877 and the Battle of Blair Mountain in 1921.