The actual name of Butch and Sundance's gang was The Wild Bunch. However, when the Sam Peckinpah film, The Wild Bunch, was released a few months earlier, the name of the gang was changed to the Hole in the Wall Gang to avoid confusion with Peckinpah's film.
The bull's name in the film is "Bill". He was flown in from Los Angeles for the bicycle scene, which was shot in Utah. In order to make Bill charge, the filmmakers sprayed a substance on his testicles. Oddly, he didn't seem to mind and endured it through several takes (from The Making of 'Butch Cassidy and the Sundance Kid').
The climactic gun battle at the end of the movie was historically inaccurate. There were only a few uniformed police officers/officials present during the shootout (the rural town of San Vicente in southern Bolivia, where Cassidy and Sundance were supposedly killed, was a very small place back in November 1908, and didn't have many police officers). Plus, there were only three Bolivian soldiers who actually took part in the fight alongside the local police, not the hundreds shown in the film. In addition, the casualty count among the Bolivian policemen was nowhere near as enormous as shown (only one soldier and one police official were actually killed, plus another soldier and an unknown number of policemen and some local posse members were wounded), and most of the gun battle took place in the evening and at night, not in broad daylight as shown in the movie. These were the main reasons why the Bolivian government at first banned the film from being shown in that country.
The filmmakers tried to get Bob Dylan to sing Burt Bacharach's famous song for the movie. He declined.
The now-famous leap off the cliff to elude capture was done earlier by Tyrone Power as Jesse James in the 1939 film Jesse James.
The real "Hole in the Wall Gang" hid in Brown's Park near the Green River. One of their bank robberies occurred in Delta.
The river jump was shot at the studio's Century Ranch near Malibu, CA. Paul Newman's and Robert Redford's stuntmen actually jumped off of a construction crane by Century Lake. The crane was obscured by a matte painting of the cliffs. Newman and Reford start the jump in Colorado, but only land on a mattress.
The sister of the real Butch Cassidy often visited the set, and her presence was welcome to the cast and crew. During lulls in shooting she would tell stories about her famous brother's escapades, and was amazed at how accurately the script and Paul Newman portrayed him. Before the film was released, the studio found out about her visits and tried to convince her to endorse the movie in a series of ads to be shown in theatres across the country. She said that she would, but only if she saw the film first and truly stood behind it. The studio refused, saying that allowing her to see the film before its release could harm its reputation. Finally, at Robert Redford's suggestion, she agreed to do the endorsements - for a small "fee."
This movie was filmed roughly the same time as Hello, Dolly!, on the sound stage next door. Director George Roy Hill believed that the studio would allow him to film the New York scenes on "Dolly's" sets, since the two films' daily shooting schedules were totally different. After production started, though, the studio informed him that it wanted to keep the sets for "Dolly" a secret and so refused him permission. To work around this, Hill had Robert Redford, Paul Newman and Katharine Ross simply pose on the sets and took photos of them. He then inserted images of the three stars into a series of 300 actual period photos and spliced the two different sets (real and posed) together to form the New York montage.
Two fictional western characters may have been derived from the name Butch Cassidy (1866-1908): Butch Cavendish, the arch rival of The Lone Ranger, and good guy Hopalong Cassidy, whose popularity exceeded many western heroes in the 1940s and 50s.
With nine wins it currently holds the record for the British Academy Awards (BAFTAs). It won for picture, actor (Robert Redford), actress (Katharine Ross, direction (George Roy Hill, screenplay, cinematography, film editing, sound and score.