Director Robert Rossen filmed in an unusual manner. Nobody in the cast had a script. Rossen let them read it once and took it away from them. According to Broderick Crawford, "We really had to stay on our toes."
Al Clark did the original cut but had trouble putting all the footage that Robert Rossen had shot into a coherent narrative. Robert Parrish was brought onboard by Rossen and Harry Cohn, to see what he could do. Since Rossen had a hard time cutting anything he shot, after several weeks of tinkering and cutting, the movie was still over 250 minutes long. Cohn was prepared to release it in this version after one more preview, but this threw Rossen into a panic, so Rossen came up with a novel solution. Rossen told Parrish to "[s]elect what you consider to be the centre of each scene, put the film in the synch machine and wind down a hundred feet before and a hundred feet after, and chop it off, regardless of what's going on. Cut through dialogue, music, anything. Then, when you're finished, we'll run the picture and see what we've got". When Parrish was done with what Rossen had suggested, they were left with a 109-minute movie that was more compelling to watch. After the film won its Academy Award for Best Picture, Cohn repeatedly gave Parrish credit for saving the film, even though Parrish only did what Rossen told him to do.
Mercedes McCambridge was cast after she got angry with the producers. She and other actresses were kept waiting in an office in New York City during open auditions. McCambridge told the producers off and stormed out of the office. They called her back and eventually cast her because she fit the part of Sadie.
According to Broderick Crawford, "During the filming, we never mentioned the name of Huey Long on the set. That was the unspoken law at the studio."
Mercedes McCambridge's Best Supporting Actress Oscar win is one of the rare occasions where an actor or actress has won an Academy Award in their film debut.