Henry McCarty was born in New York City in 1859, far from the West where he would eventually become a famous outlaw. In 1877, McCarty adopted the pseudonym "William H. Bonney" and later became known as "Billy the Kid" or simply "The Kid."

He was 15 years old when his mother died and his stepfather abandoned the family, leaving both McCarty boys orphans. Sarah Brown, the owner of a boarding house, gave them room and board in exchange for work.

Billy's first encounter with the law came in 1875, when he helped a man by the name of "Sombrero Jack" steal clothing from a Chinese laundry. The crime only carried a minor sentence, but rather than face punishment, the wiry youth escaped the jailhouse by shimmying up a chimney.

Billy wasn't always engaging in illegal activities. He once worked in a cheese factory--at least according to Charlie Bowdre, who would later be in Billy's posse, and was part owner of the cheese factory. Bowdre's descendants have said this is where the two of them met.

On August 17, 1877, McCarty was at a saloon in Bonita, Arizona, when he got into an argument with Francis P. "Windy" Cahill, a blacksmith who reportedly had bullied McCarty and called him a "pimp". McCarty in turn called Cahill a "son of a bitch", whereupon Cahill threw McCarty to the floor and the two struggled for McCarty's revolver. McCarty shot and mortally wounded Cahill. A witness said, "[Billy] had no choice. He had to use his equalizer." Cahill died the following day.

After killing Cahill, McCarty stole a horse and fled Arizona Territory for New Mexico Territory, but Apaches took the horse from him, leaving him to walk many miles to the nearest settlement. At Fort Stanton in the Pecos Valley, McCarty--starving and near death--went to the home of friend and Seven Rivers Warriors gang member John Jones, whose mother Barbara nursed him back to health.

When Billy's employer John Tunstall was murdered for daring to challenge the local monopoly of pretty much everything, Billy and other Tunstall employees formed a ragtag vigilante army called The Regulators and launched a guerrilla-style insurrection that became known as the Lincoln County War of 1878. Billy and two other Regulators were later charged with killing three men, including Lincoln County Sheriff William J. Brady and one of his deputies. The war was fictionalized by several Hollywood movies, including The Left Handed Gun (1958), Chisum (1970), Pat Garrett and Billy the Kid (1973), and Young Guns (1988).

Unlike other Old West outlaws such as Jesse James, Cole Younger, or Butch Cassidy, Billy the Kid didn't make his living as a bandit. The young gunslinger stole the occasional horse, but he never once held up a bank, train or even a stagecoach. Outside of his gunfighting days with the Regulators, his main criminal enterprise was rustling cattle on the New Mexico plains.

According to Dr. Henry F. Hoyt, a friend of Billy's who was working in the Exchange Hotel in Las Vegas, New Mexico, in 1879, he ran into Billy and a companion the Kid referred to as "Mr. Howard from Tennessee." The Kid later told Hoyt that "Mr. Howard" was actually Jesse James, who was in town visiting a boyhood friend from Missouri. The Kid claimed Jesse offered him a job robbing trains, but that he had replied it was not his line of business.

Billy himself reportedly claimed he had killed 21 men--"One for every year of my life." But a reliable contemporary authority estimated the actual total as nine: four on his own and five with the aid of others.