The Pinkerton National Detective Agency, usually shortened to the Pinkertons was a private U.S. security guard and detective agency established by Allan Pinkerton in 1850. Pinkerton had become famous when he foiled a plot to assassinate president-elect Abraham Lincoln, who later hired Pinkerton agents for his personal security during the Civil War (although at the time of Lincoln's assassination, his security was no longer handled by Pinkerton, but by U.S. Army personnel). Pinkerton's agents performed services ranging from security guards to private military contracting work. During its height, the Pinkerton National Detective Agency employed more agents than the standing army of the United States of America, causing the state of Ohio to outlaw the agency due to fears it could be hired out as a private army or militia.

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