After the crew was thrown out of East Prairie, MO, by the chief of police (for allegedly being "communists"), Roger Corman realized that he needed one more wide shot of the high school. He and an assistant went back into the town and hurriedly filmed the shot. The chief must have gotten wind of his being there, as he was seen by Corman arriving in the distance. Corman and his assistant quickly threw the camera and equipment into their car, and sped away in the opposite direction, unscathed.
In his 2022 book "Boldly Go", William Shatner recounts that locals were hired to be extra's during the filming of Cramer's big racist speech on the courthouse steps. But because Shatner had done a lot of shouting the previous day, he had to spare his voice for most of the day. Roger Corman told him to mime the speech while he gave direction to the crowd on how to react as he shot over Shatner's shoulder. By the end of the day, Shatner's voice had recovered enough for him to perform the speech during his close-ups. At this time, most of the extra's had already left the set on their own accord. The following day, a local newspaperman came up to Shatner and Corman and told them they were smart not to perform the actual dialogue in front of the crowd. He explained that a tree in the courthouse yard had been used for lynchings no less than twenty years earlier, and that some of the extras in the crowd had been part of that hanging. If they had heard the speech, there was no telling how they might have reacted.
Roger Corman said this film changed a lot of his feelings about filmmaking. It went to festivals and got really great reviews, but it was the first movie he made that lost money. After analyzing why, he realized it had too much of lesson it was trying to teach the audience. From that point on, he focused more on entertaining them instead. He said he always tried to put a moral in his films after that, he just kept it subtle without pounding it into the audience because that isn't why they go to movies.
Shot entirely on location in southeast Missouri with locals acting as extras. Knowing how incendiary the script was, Roger Corman made a point of not showing them the full screenplay, for fear of being run out of town.
William Shatner said that their lives were threatened, equipment was sabotaged and permission to film in a local schoolyard was revoked.