Nobody in the cast had a script; director Robert Rossen let the actors 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 turning the footage into a coherent narrative. Robert Rossen and Harry Cohn brought Robert Parrish on board to see what he could do. Rossen had a hard time cutting anything he shot, and after several weeks the movie was still over 4 hours long. Cohn was prepared to release the cut after one more preview, throwing Rossen into a panic. Rossen told Parrish "select what you consider to be the core of each scene, put the film in the sync machine and wind down 100 feet before and 100 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, they were left with a 109-minute movie. After the film won an 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's Best Supporting Actress Oscar win is one of the rare occasions where an actor or actress has won an Academy Award for a film debut.
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. In a huff, she 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 perfectly.
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."