Rip Torn was originally cast in the role of George Hanson. According to Torn, Dennis Hopper pulled a knife on him during a pre-production meeting. On The Tonight Show with Jay Leno (1992), Hopper claimed it was Torn who pulled the knife. Torn sued Hopper for defamation and won.
Stephen Stills wrote the song "Find the Cost of Freedom" at Dennis Hopper's request, for use with the final scene (when the camera pans up into the sky). Hopper ended up not using it, and the song was eventually released as the B-side to Crosby Stills Nash & Young's single "Ohio". CSNandY often used it to close their concerts.
During Jack Nicholson's "UFO" speech, Dennis Hopper was intent on getting him very stoned on marijuana. The laughing that eventually broke up his speech was not planned, and when Nicholson repeats the line "it . . . it . . . would be devastating . . . " it was the next take.
Both the Captain America bike and the Billy Bike were designed and built by an African-American bike builder named Ben Hardy. Peter Fonda met Hardy when Hardy built the bike he rode in The Wild Angels (1966). Dennis Hopper is interviewed in the documentary "History of the Chopper" and confirms that it was Hardy who built the bikes. One of the people who worked on the bikes was Dan Haggerty, who later starred in The Life and Times of Grizzly Adams (1977).
For the famous soliloquy that Peter Fonda does in the cemetery while tripped on acid, Director Dennis Hopper asked Peter to talk to the statue as if he were talking to his mother, who died a suicide when Peter was 10 years old. Peter didn't want to do it, as he had never confronted his feelings about his mother. But Hopper insisted, which is why you hear Peter call the statue "Mother", and he states that he both loves her and hates her, which expresses his conflicted emotions. This scene persuaded Bob Dylan to allow the use of his song "It's Alright Ma" in one of the final scenes, which contains lyrics referencing suicide. Peter told Dylan, "I need to hear those words", and he agreed to its use.
Peter Fonda was an experienced motorcycle rider and the bike he rides in the movie is seriously stretched and raked and has tall "apehanger" style handlebars. Dennis Hopper was not as experienced a rider, therefore his bike is less radically chopped.
Peter Fonda wore the Captsin America jacket and rode his chopper a week around Los Angeles before shooting began to give them a broken-in look and to get used to riding the radically designed bike. The American flag on the back of the jacket and on the gas tank of the bike caused him to be pulled over several times by the police.
Dennis Hopper had the original cut of the film at an estimated three hours in length. Upon reviewing it with some of the other key members of the production staff the length was cut down to its current length.
The New Orleans cemetery is St. Louis #1, a Catholic cemetery. They didn't have permission to shoot there and Catholic audience members were shocked that the church had allowed it. Since then no other films have been allowed to shoot at St. Louis #1, unless it's a documentary and you have permission. Interview with the Vampire: The Vampire Chronicles (1994), Double Jeopardy (1999) and other films since then have all used the Lafayette Cemetery, which is Protestant.
The rednecks in the Louisiana coffee shop who taunt the boys, and the two in the pickup truck at the end of the movie, were all local residents recruited by the filmmakers. In the case of the coffee shop denizens, the filmmakers were preparing to audition a group of local theater people when Dennis Hopper saw Buddy Causey Jr., Duffy Lafont and several others watching them and making wisecracks and decided to use them instead.
It was one of the first films to make extensive use of previously released musical tracks rather than a specially written film score. This is common with films now but was quite unusual at the time (the exception being The Beatles films and some other special cases).
Dennis Hopper and Peter Fonda did not write a full script for the movie and made most of it up as they went along. They didn't hire a crew but instead picked up hippies at communes across the country, and used friends and passersby to hold the cameras and were drunk and stoned most of the time.
The swimming scene (Billy and Wyatt go swimming with two commune girls) was shot at two different times. When they shot the scene Peter Fonda was in the hospital. You can't see him together with Dennis Hopper or one of the girls in the entire scene. The legs you see are from a stand-in. The images of Fonda were shot separately, weeks later.
Dennis Hopper was going through a very bad time during production. He was in a state of drug-induced paranoia and he screamed at everyone. Crew members secretly recorded his tirades and sent the tapes to the production company in Los Angeles to explain why so many of them quit the film.
Peter Fonda got the idea for this movie after seeing a picture of himself and Bruce Dern on their motorcycles. He got Dennis Hopper (who was planning to get out of the acting business and become a teacher at the time) involved when he promised him he could direct the film.
The 1962 1200 cc Harley's driven by the main characters in the film were actually purchased from the Los Angeles Police department. Harley-Davidson refused to provide free bikes for the film because "The protagonist were outlaws and they thought it was bad for their image." according to an article that appeared in the June 2005 edition of the History Channel magazine.
The bridge seen in the opening credits, the Old Trails Arch Bridge in Topcock, AZ, is the same bridge Peter Fonda's father, Henry Fonda, playing Tom Joad, crossed with the Joad family when entering California in The Grapes of Wrath.
Captain America's (Peter Fonda's) chopper was so "squirrely" to ride that at one point Jack Nicholson (who was on the back) squeezed his knees on Fonda's side to balance himself and broke one of Fonda's ribs.
The trivia item below may give away important plot points.
There were 2 bikes used for Captain America, one was stolen the other was burned in the end of the movie. The burned bike was later restored by Peter Fonda and was sold to John Parham and can be seen in the National Motorcycle Museum in Anamosa Iowa.