On 24th June, 1889, Butch Cassidy, Tom McCarty and Matt Warner, held up the San Miguel Valley Bank. Over the next few years Cassidy's gang robbed banks in Idaho. The gang eventually escaped to the Robbers' Roost in Utah. Cassidy now formed a new gang that became known as the Wild Bunch. This include Harry Longbaugh (the Sundance Kid), Ben Kilpatrick, Harvey Logan, William Carver, George Curry, Laura Bullion, Elza Lay and Bob Meeks.

The name Wild Bunch was misleading as Cassidy always tried to avoid his gang hurting people during robberies. His gang were also ordered to shoot at the horses, rather than the riders, when being pursued by posses. Cassidy always proudly boasted that he had never killed a man. The name actually came from the boisterous way they spent their money after a successful robbery.

On 2nd June, 1899, Cassidy, Curry, Logan and Lay took part in the highly successful Union Pacific train holdup at Wilcox, Wyoming. After stealing $30,000 the gang fled to New Mexico. On 29th August, 1900, Cassidy, with the Sundance Kid, Logan and Carver, held up the Union Pacific train at Tipton, Wyoming. This was followed by a raid on the First National Bank of Winnemucca, Nevada (19th September, 1900) that netted $32,640. The following year the gang obtained $65,000 from the Great Northern train near Wagner, Montana.

George Curry was killed by Sheriff Jesse Tyler on 17th April, 1900. The following year William Carver and Ben Kilpatrick were ambushed by Sheriff Elijah Briant and his deputies at Sonora, Texas. Carver died from his wounds three hours later. Kilpatrick escaped but he was captured in St Louis with another gang member, Laura Bullion, on 8th November, 1901. Kilpatrick was found guilty of robbery and was sentenced to 15 years in prison. Another gang member, Harvey Logan was captured on 15th December, 1901.

Butch Cassidy and the Sundance Kid began to think that being an outlaw in America was becoming too dangerous and in 1902 decided to start a new life in South America.