thumb|left|Logo of the Pinkerton National Detective Agency In the United States, Allan Pinkerton established the Pinkerton National Detective Agency – a private detective agency – in 1850. Pinkerton became famous when he foiled a plot to assassinate then President-elect Abraham Lincoln in 1861. Pinkerton's agents performed services which ranged from undercover investigations and detection of crimes, to plant protection and armed security. At the height of its existence, the number of Pinkerton National Detective Agency active agents and reserves rivaled the number of active soldiers and reserves in the United States Army."Our History: Our roots trace back to 1850," Pinkerton Consulting & Investigations, 2021. (Quote from webpage: "1890s: Pinkerton's National Detective Agency has 2,000 active agents and 30,000 reserves.") Retrieved 16 Aug 2021."The U.S. Army in the 1890s," U.S. Army Center of Military History, Apr 2000. (Quote from website: "Of the roughly 2,100 officers and 26,000 enlisted men in the Army on 1 Apr 1898. . .") Retrieved 16 Aug 2021. Allan Pinkerton hired Kate Warne in 1856 as a private detective, making her the first female private detective in America.
thumb|left|logo of the pinkerton national detective agency in the united states allan pinkerton established the pinkerton national detective agency – a private detective agency – in 1850 pinkerton became famous when he foiled a plot to assassinate then president-elect abraham lincoln in 1861 pinkerton's agents performed services which ranged from undercover investigations and detection of crimes to plant protection and armed security at the height of its existence the number of pinkerton national detective agency active agents and reserves rivaled the number of active soldiers and reserves in the united states army"our history our roots trace back to 1850" pinkerton consulting & investigations 2021 (quote from webpage "1890s pinkerton's national detective agency has 2000 active agents and 30000 reserves") retrieved 16 aug 2021"the us army in the 1890s" us army center of military history apr 2000 (quote from website "of the roughly 2100 officers and 26000 enlisted men in the army on 1 apr 1898  ") retrieved 16 aug 2021 allan pinkerton hired kate warne in 1856 as a private detective making her the first female private detective in america