Answer
The first known private detective agency was founded by Eugène-François Vidocq in 1827. Vidocq was a former criminal who had turned himself in to the police and become an informant. He used his knowledge of the criminal underworld to help the police solve crimes, and he eventually started his own agency to provide private detective services. Vidocq's agency was successful, and he became known as the "Father of Modern Detectives".