The murder and rape of Madge Oberholtzer by D.C. Stephenson is what did the Klu Klux Klan in, atleast in my Home state of Indiana (I dont particularly know about the History of the Klan in other states). Before 1925 250,000 Klansmen resided in Indiana (or 30% of Native born Adult Male Hoosiers) and they gained about 2,000 New Members per week. D.C. Stephenson was the very Influential Grand Dragon of the Indiana Klan, In 1923 the Indiana Klan broke away from the national organization making it a separate entity. Stephenson was considered the most powerful man in Indiana (Half of the elected members of the Indiana General Assembly and the Governor were members of the Klan). In 1925 Stephenson, head of the Indiana Klan, met Madge Oberholtzer, the head of the state's commission to combat illiteracy. The night of the inaugural ball of Republican Governor Edward L. Jackson (A Klan member), she was abducted from her home, taken to the  Indianapolis train station, and held in a private railroad car. On the train to Hammond Indiana, Stephenson raped her repeatedly and attacked her. In Hammond, she pleaded the need to get to a drug store, where she secretly ate mercury  tablets. Using the illness brought on by the poisons as an excuse, she begged Stephenson to release her. He took her back to Indianapolis and held her at his place. After Oberholtzer refused to marry him several days later, he had her returned to her home and secretly placed in bed. When her parents found her, the young woman was nearly dead. Taken to the hospital, Oberholtzer died about a month later. She told her story in detail to several witnesses. Stephenson was immediately arrested and charged with second-degree murder. The attending doctor, who testified in the trial, said that Oberholtzer's wounds appeared as if a "Cannibal had chewed on her". The prosecution held that the wounds and mercury together caused the death of Oberholtzer. Stephenson was convicted and the State Supreme Court upheld the decision in Stephenson v. State of Indiana. He was sentenced to Prison. When the word broke out about his Vile Character, members dropped out by the tens of thousands (Afterall the so called defender of Protestant Womanhood had murdered a Protestant White Women). Stephenson soon started ratting out the Klan to the Indianapolis Times and released a list of elected and other officials who had been in the pay of the Klan. When the Second Scandal about corruption occurred tens of thousands remaining members dropped out aswell. By the end of the decade, the Klan was down to about 4,000 members (In Indiana) and finished in the state. Efforts by some to revive it in the period of the 1960s and 1970s were not successful. I hope this dark time in my Beautiful Homestates history, has helped answer your question.