Allan Pinkerton (August 25, 1819 – July 1, 1884) was a U.S. detective. He was born in Glasgow, Scotland to police sergeant William Pinkerton and his wife Isabell. Allan emigrated to the United States in 1842. In Chicago, Illinois in 1852, he formed the first detective agency, the Pinkerton Agency, which solved a series of train robberies. He was head of the U.S. Secret Service in 1861–1862 and foiled an assassination plot in Baltimore, Maryland, while guarding Abraham Lincoln on his way to his inauguration for his first term as president. He was so famous that for decades after his death, the word "Pinkerton" was a slang term for a private eye.