2. HISTORY

Before the 19th century, there were few municipal police departments, though the first had been created in Paris in 1667. As police activities moved from appointees helped by volunteers to professionals, the idea of dedicated detectives did not immediately arise. The first private detective agency was founded by Eugène François Vidocq in Paris in the early 1800s, who had also headed a police agency in addition to being a criminal himself. Police detective activities were pioneered in England by the Bow Street Runners and later the Metropolitan Police Service in Greater London. The first police detective unit in the United States was formed in 1846 in Boston.

Used from: https://en.wikipedia.org/wiki/Detective