The film was shot entirely on location in Mexico. One day during a break in filming Charles Bronson and Ernest Borgnine decided to go to the nearest town for cigarettes. This meant saddling up in costume, sidearms and all, and riding to town. On the way the pair was spotted by a truck full of "federales"--Mexican federal police--who, mistaking them for bandits, stopped them and held them at gunpoint until representatives from the film company showed up to vouch for them.
For being made in the mid-1950s, this film has a quite fast cutting rate. In 90 minutes of action, it contains about 1130 edits and other transitions. This equates to an average shot length of just under five seconds.
Eli Wallach has said that the Mexican government was so upset about the negative portrayal of Mexicans in the film that they insisted that the making of The Magnificent Seven (1960) be monitored by censors.
One of the first major Hollywood films to be made on location in Mexico. Filmmaking legislation in Mexico meant that a local director had to be involved in the production in some capacity, though he wasn't actually used.
Robert Aldrich was so keen on this period of history that he planned to shoot a biopic of Emperor Maximilian. In 1964, he announced that he would begin filming after The Flight of the Phoenix (1965) but it failed to materialise.
First film released in the "SuperScope" wide-screen process. Shot at a conventional 1.37:1 aspect ratio, the film was cropped to 2:1 in post-production, given a CinemaScope-compatible (2x) squeeze and blown up to normal frame height. SuperScope was designed to achieve anamorphic prints from standard flat 35mm negatives. The MGM DVD approximates the 2:1 release print aspect ratio. SuperScope was the fore-runner of "Super 35".
In her biography "Playing the Field," Mamie Van Doren claimed Burt Lancaster interviewed her for the role of the Countess and attempted to seduce her. She told him she did not wish to get the part in that way and that her mother was waiting for her outside in the car. Lancaster told her she was right and gave her the script to study, and although she officially auditioned, she didn't get the part.
The Mexican authorities were appalled at the way their citizens were depicted in the film so any subsequent Hollywood productions had to conform to some strict rules. This explains why in The Magnificent Seven (1960), the locals are all wearing pristine white clothes.
In his biography, Ernest Borgnine reports that, during the shooting, Burt Lancaster brought his children on the set and all of them laughed at Jack Elam because of his walleyed eye. Elam of course was upset because of this and he had a tough argument against Lancaster in a fierce fist fight.