The Rolling Stones had gotten the idea of using the Hell's Angels as security because they had used the London chapter of the club as security during their free concert at Hyde Park that past July. However, the British chapter was not as violent as their American counterparts.
According to Albert Maysles (in 1999 while he visited UCLA), George Lucas was one of the cameramen for this shoot. Unfortunately his camera jammed after shooting about 100 feet of film that night. All of his footage was deemed unacceptable and wasn't used in any version of the final product.
Contrary to popular belief, Meredith Hunter was not killed during the performance of "Sympathy for the Devil". He was actually stabbed just as The Rolling Stones started the first verse of "Under My Thumb". The version of "Under My Thumb" that appears in the film was actually played after the killing with the stabbing moved to the end of the second version of the song.
In the original version, played to theatre audiences, Mick Jagger used foul language on two or three occasions - appropriate for the moment but later censored out for TV broadcast with a "guitar strum" sound overdub to block the "offending" word. Only early copies of the film contain the original uncensored dialogue.
A rough demo version of the classic "Brown Sugar" is heard in the sequence detailing The Rolling Stones stay at Muscle Shoals. According to 'Bill Wyman' in his book on his days in the band, the Stones performed the song for the very first time in front of an audience at Altamont.
After viewing footage of the stabbing of Meredith Hunter police identified Alan Passaro, a local Hell's Angel, as the man who did the stabbing, arrested him and charged him with murder. At his trial, however, closer examination of the footage showed that Hunter had pulled a gun before Passaro pulled his knife. Passaro was acquitted on grounds of self-defense.
Michael Lang, who was one of the promoters responsible for Woodstock, was also one of the promoters for Altamont. He is seen being interviewed about the building of the stage, as well as onstage during the concert.
The concert originally was originally going to be held at Golden Gate Park in San Francisco, but the city wouldn't give a permit after hearing that The Rolling Stones would be on the bill and feared a huge crowd. The concert was then moved to Sears Point (now Infineon) Raceway in Sonoma, but after a dispute with the track's owner, the stage and all the sound equipment was moved to Altamont within 24 hours before the concert was to take place.
Besides "Brown Sugar", two other songs that were unreleased at the time are heard during the scenes filmed at Muscle Shoals. They were "Wild Horses" and "You Got to Move". Those songs, along with "Brown Sugar" would be released on the classic "Sticky Fingers" album that came out two years later in 1971.
The Grateful Dead also used the Hell's Angels as security for several of their concerts. However, the Angels that were at Altamont were later revealed to be neophytes and hardly any of the leaders were present at the show.
It was reported in the San Jose Mercury that the California Highway Patrol observed heavy traffic from as far away as Bakersfield caused by cars headed to this concert. If current laws were enforced in 1969, The Rolling Stones would have received a bill from the California Highway Patrol and other law enforcement agencies for traffic enforcement duties related to this event.
The opening scenes of the movie with the donkey are the photo shoot for what would be come the cover of "Get Yer Ya-Yas Out". Several earlier concert scenes filmed at Madison Square Garden made it onto that album. Albert Maysles and David Maysles filmed the Madison Square Garden shows; they form part of this movie.
Legendary Punk guitarist Johnny Thunders is in the crowd during the Rolling Stones first performance. At Mick's line "Let's have a look at you New York", Johnny is the figure playing with his long black hair sitting on someone's shoulders.
When the Stones were recording at Muscle Shoals, they did it pretty much in secret due to the fact that they didn't have the proper work visas to allow them to do any any recording in the United States.