Billy the Kid, born Henry McCarty and also known as William H. Bonney, was an infamous and iconic outlaw and gunman of the Old West. Born to an Irish-American family in New York City and left home at an early age. Known for his participation in the Lincoln County War and later became a infamous cattle rustler and murderer. Was killed at the age of 21 by Pat Garrett, though Billy was little known during his lifetime, Garrett helped make the little known outlaw a legend after he published The Authentic Life of Billy, the Kid .