They Won't Forget is a 1937 film directed by Mervyn LeRoy. It was based on a novel by Ward Greene called Death in The Deep South, which was in turn a fictionalized account of a real life case: the trial and subsequent lynching of Leo Frank after the murder of Mary Phagan in 1913. Lana Turner made her film debut as the murder victim. Wikipedia
Confederate Veteran: (to his fellow Confederate veterans) On your feet now. Go on and look sharp. The whole town's wwatching. This is the one day out of the year that belongs to us.