Allan Pinkerton was a Scottish-American detective and spy who founded the Pinkerton National Detective Agency in 1850. He is best known for his work as a private detective, often taking on cases involving train robberies and labor disputes. He also served as a Union spy during the American Civil War. His agency was the first to offer services such as undercover investigations and surveillance. Pinkerton's legacy lives on today, with the Pinkerton National Detective Agency still operating in the United States.