Charles A. Siringo 
Two Evil Isms, Pinkertonism and Anarchism 
by a Cowboy Detective Who Knows, as He Spent Twenty-two Years in the Inner Circle of Pinkerton’s National Detective Agency (1915)

’Siringo…the shrewd cowboy detective lived a life filled with adventure among the underworld characters such as murderers, moonshiners, rustlers, dynamiters and other criminals.’ -Wichita Falls Times, June 29, 1969

’In 'Two Evil Isms, ’ he boldly says that Horn was hired by the agency to help 'wealthy cattlemen get rid of small ranchmen’ at $600 a head. The latest biography of Tom Horn corroborates the statement.’ -January 22, 1950

The author served with the Pinkerton National Detective Agency for twenty-two years, and he publishes revelations from the inside.

These stories of the methods of the Pinkertons were so objectionable to the private detectives that Mr. Siringo has been subjected to persistent persecution. Efforts have been made to exclude his book from the mails; and he himself has been arrested on warrants charging him with libel.

In his book, Mr. Siringo deals with Chicago anarchist cases, the Coeur D’Alene riots, the Haywood trial, and many other thrilling episodes of crime.

Mr. Siringo’s description of the slavery system of the Rockefellers and other Coal Kings in Colorado: his flash-lights on the custom of politicians who hire private detective agencies to corrupt voters; his exposures of how juries were fixed, and witnesses either found or lost, constitute a moving picture showing of ways of 'playing the game’ in the early 1900s.