Allan Pinkerton was born in the Glasgow, Scotland to Isobel McQueen and William Pinkerton. The house that the family lived for most of Pinkerton’s life is now a Mosque. It is call the “Glasgow Central Mosque”.
In 1849, Pinkerton was appointed as the very first detective in Chicago. In the 1850s, Pinkerton partnered with Edward Rucker, a Chicago attorney, form the North-Western Police Agency. This agency was later changed to “Pinkerton National Detective Agency”. This agency is still in existence today as Pinkerton Consulting and Investigations.
Prior to his service with the Union Army, he developed several investigative techniques that are still used today. Among them are "shadowing" (surveillance of a suspect) and "assuming a role" (undercover work). Shortly after the Civil War, Pinkerton served as head of the Union Intelligence Service in 1861–1862 and foiled an alleged assassination plot in Baltimore, Maryland, while guarding Abraham Lincoln on his way to his inauguration. Pinkerton and his agents often worked undercover as Confederate soldiers and sympathizers, in an effort to obtain military intelligence. Pinkerton served in several undercover missions under the alias of Major E.J. Allen. Pinkerton was succeeded as Intelligence Service chief by Lafayette Baker. The Intelligence Service was the forerunner of the U.S. Secret Service.
Following Pinkerton's service with the Union Army, he pursued his law enforcement skills and focused on train robbers, such as the Reno Gang and the infamous outlaw Jesse James. He was initially to track down Jesse James, but after Pinkerton failed to capture him, the railroad withdrew their financial support and Pinkerton continued to track James at his own expense. After James allegedly captured and murdered one of Pinkerton's undercover agents who was undercover and worked at the farm neighboring