The majority of the outdoor scenes were shot in and around the University of California, Irvine campus, which was designed by futurist architect William L. Pereira, and was only six years old at the time of filming. Much of the production centered around the Social Science complex, which was designed by A.C. Martin & Associates and was still under construction during filming. Careful use of camera angles and editing made a handful of buildings and exteriors feel more like action spread across an entire city.
Some exteriors, and all of indoor sets were all filmed at the Fox backlot in Century City, Los Angeles.
The script opened with a fugitive ape being shot by the police. As they walked to it, the body would be revealed to be covered in open wounds and scars, showing the horrible living conditions of the slave apes. This was cut, again, for being too gruesome.
This is the only film from the original Planet of the Apes (1968) series of five that was not rated G, and the only entry released without a pre-title sequence. Reason: the opening was deemed too violent, and the producers wanted to avoid an R rating. The opening showed police on night patrol shooting an escaped ape and discovering his body covered with welts and bruises that are evidence of severe abuse. (Governor Breck and MacDonald refer to this incident in a scene that survived the final cut.) That and many other bloody images were deleted after a pre-release print was shown to a preview audience. The opening scene appears in the novelization and the comic book adaptation of the movie. On November, 2008, the Blu-Ray unrated version restored many of those graphic scenes, but not the pre-credit opening (after the film was re-edited, some shots from the deleted opening were used in a later scene added that had Caesar captured at night, probably the reason the opening was never resurrected on disc).
The jumpsuits worn by the apes (to save the cost of fake fur for the crowd of ape extras) were leftover costumes from the 1964-68 Fox TV series Voyage to the Bottom of the Sea (1964). The Ape Management men's insignia patches and computer and electronic cabinets, all came from the Irwin Allen series, The Time Tunnel (1966). The large set that comprised Ape Management Center (where apes are processed and trained to become docile servants) is a re-dressed set of Adm. Matthew's office and the Triton Control complex from City Beneath the Sea (1971). Governor Breck's Ape Auction throne was first used in Taylor's spaceship in Planet of the Apes (1968). The same style chair is also used by passengers on the space-plane in Land of the Giants (1968). The same chairs were used in the Earthforce Spaceships in the TV series Babylon 5 (1993).
In the film (set in 1991), the apes were enslaved after a plague brought back from space wiped out all of the Earth's cats and dogs a decade earlier before the events portrayed. In 1978, six years after the film's release, there was a worldwide pandemic of canine papillomavirus (a disease not known until then) that killed several thousands of dogs.
Writer Paul Dehn conceived the film as a simian take on the American Civil Rights movement of the time. Ironically, Dehn was English but brought an astute sensibility to the project. (Not surprisingly, the film was very popular with black audiences.)
The budgets on the Apes movies were constantly trimmed because 20th Century Fox was still in financial trouble following the huge flops of Cleopatra (1963), Star! (1968) and Hello, Dolly! (1969). One of the results of the lower budget was the reuse of music cues throughout this film and "Battle for the Planet of the Apes" (1973) ("Escape From the Planet of the Apes" (1971) repeated only one piece of music in the film).
The idea of a continuing franchise of sequels (other than spy films) was quite a novel one to 1970s audiences, although the budgets kept decreasing with each successive film. This was mainly noticeable with the limited amount of ape characters using John Chambers' make-up. Most wore pull-over masks.
All five original "Planet of the Apes" movies were #1 at the U.S. box office when released. "Conquest of the Planet of the Apes" spent one week as the #1 top grossing film: the week of July 2, 1972 it made $4,395,549.
To promote this movie Twentieth Century Fox arranged a bizarre publicity stunt: a contest held in Century City to find "Miss Beautiful Ape" from among five young women wearing ape masks. The master of ceremonies for the contest was Gary Owens.
In the previous film, Escape from the Planet of the Apes, Zira and Cornelius name their son "Milo". However in the start of the film, Armando calls him "Caesar", which contradicts it and is therefore probably a mistake. Futhermore, the name of the ape Milo is swapped for near the end of Escape, is "Salomé", so either Armando changed his name, he is not the same ape, or it's a mistake. (Note: Armando had to change the name, as "Milo" had been the name of one of the "Ape-O-Nauts", which would've aroused suspicion).
Director J. Lee Thompson tried to frame every shot as wide as possible and use strong primary colors of black and red during the revolt to conceal subpar ape makeup and make it appear as though an army of hundreds was clashing throughout the city when actually only dozens of extras were used over a few blocks.
The chimpanzee cook is played by Lou Wagner, who had portrayed Lucius in the original Planet of the Apes (1968). When he is adding kerosene to a frying pan over a flame, it ignites in flames as he pulls it back off the flame. The flames can be seen going over his hands (most likely his stunt double's) and up around his head.
The cast includes both Roddy McDowall and Paul Comi, who had co-starred as Earth astronauts who land on Mars in the 1960 episode of the original version of The Twilight Zone (1959) titled "People Are Alike All Over." Although it is McDowall's character Cornelius from the preceding "Apes" film (along with Kim Hunter's Dr. Zira and Sal Mineo's Dr. Milo) portraying an astronaut, it could be argued Roddy's character in this film, the son of Cornelius, may also have been considered an astronaut, as he had been conceived before his parents' spaceflight.
This film's score was done by soul artist Tom Scott, with the exception of the final piece of music at the film's finale which had been taken from Planet of the Apes (1968) (done by Jerry Goldsmith) from the scene where Taylor and company were running up to the scarecrows in the desert.
In several scenes during the revolution you can see that a few of the rifles carried by the apes did not have ammunition magazines in them. This would make it impossible to fire their weapons although scenes show this being done.
The trivia items below may give away important plot points.
The movie originally ended with Caesar's yell of "That day is upon you NOW!" and the apes beating Governor Breck to death despite Mr. MacDonald's plea. Poor testing resulted in the addition of Lisa yelling "NO!", which was followed by repeated footage of Caesar's speech with added dialog dubbed in by Roddy McDowall to give the film a more hopeful tone by making Caesar sympathetic and not a mass-murderer.
The second half of the final scene with Lisa begging Caesar to show mercy and him giving his "equality" speech was added after the film's completion. This is why the final shot is only of Caesar's eyes and is of a grainy quality; the shot was just a cropped piece of footage from earlier in the film. Roddy McDowall was brought in the read the final lines, which were then edited into place. Originally the film ended on a darker note, with the gorillas mercilessly beating Breck and the other human survivors to death with their rifle butts (see alternate versions). Much of the same footage exists in both endings, but in the revised version film of the apes raising their rifles is played in reverse so it appears they are lowering them, and footage of the apes beating is cut to make it appear that they are cheering.
The previous film, Escape from the Planet of the Apes (1971) had contradicted its predecessors in a significant way. In the first two films, it was established that the ape society (other than "keeper of the faith" Dr. Zaius) had completely forgotten that an intelligent human society had preceded the ape civilization. But in "Escape", Cornelius says his people knew that dumb apes had once served human masters, until the apes revolted under a defiant leader named Aldo (which was supposedly celebrated with an annual ape holiday). This film ("Conquest") and its sequel (Battle for the Planet of the Apes (1973)) carefully edit Cornelius' comments to omit the name of Aldo, and leave the implication that Caesar is the revolutionary leader. "Battle" includes a central character named Aldo, but that film is set after the ape revolution, and clearly that Aldo is not the one Cornelius referred to (who had been mentioned as being a chimpanzee in the previous film).