Cheryl and her friend, Pamella Jackson, were last seen on their way to a high school party on the evening of May 29, 1971. They visited Cheryl's grandmother in the hospital that day, then stopped and talked to some boys at a church and asked them for directions. The boys were also going to the party and Pamella and Cheryl decided to follow them there in their beige 1960 Studebaker Lark with South Dakota license plates numbered 19-3994. The car belonged to Cheryl's grandfather. They never arrived at the party, however. There has been no sign of the girls or their car since then.

The girls were considered to be runaways at first, due to their ages. Authorities initially considered the possibility that the missing teenagers may have accidentally driven their car into the Missouri River. A search of the river turned up no evidence, however. A theory that they were abducted by transients passing through the area has also been discarded.

Cheryl resided with her grandparents on Cottage Avenue in Vermillion in 1971; she moved there after her parents' divorce. Her grandmother was suffering from terminal breast cancer in May 1971, and Cheryl assisted in her care. Her grandmother was hospitalized and near death on the day Cheryl went missing, and Cheryl planned to visit her that evening. She died six days after Cheryl vanished.

Pamella and Cheryl were both employed at Dakota Hospital at the time of their disappearances. Cheryl is described as an intelligent, independent and responsible teenager. She was a good student and a member of her high school marching band. She planned to travel to California after graduating school and was saving her money for that purpose. Both girls left behind all their personal belongings, including clothes, makeup, paychecks and Pamella's hepatitis medication, when they vanished. Their families do not believe they would have run away from home, especially as Cheryl's grandmother was dying. There has been no activity on either of their Social Security numbers since they went missing.

In August 2004, police searched a rural farm eight miles southwest of Alcester, South Dakota, looking for evidence in Cheryl and Pamella's cases. The farm is only a few miles from Pamella and Cheryl's intended destination. Investigators recovered bones, photographs, clothing, and a purse among other items, but are not sure if any of these are connected to the girls' cases. At the time Pamella and Cheryl disappeared, David Lykken lived on the farm. A photograph of him is posted below this case summary. In 1971, he was seventeen years old and a student at Beresford High School, which was also where the girls attended. He knew Pamella through their church. He is currently serving a 227-year sentence in prison for kidnapping and raping a church secretary in 1990. He was also convicted of burglary in 1983. After his rape conviction, several of Lykken's former girlfriends stated he had beaten them, raped them and threatened their lives.

In 2007, Lykken was charged with murdering Pamella and Cheryl. The indictment accused Lykken of killing Cheryl in connection with rape and Pamella in connection with kidnapping. A major part of the case against him was a tape-recorded confession; Aloysius Black Crow, a cellmate of Lykken's, wore a recording device and claimed he got him to talk about the murders. Lykken's attorney maintained Black Crow was lying and Pamella and Cheryl ran away when they disappeared in 1971. In 2008, investigators discovered Black Crow had framed Lykken. He got another man to pretend to be Lykken and make statements about the alleged murders on tape. All charges against Lykken were dropped as a result, although he is still incarcerated for the 1990 rape and will not be eligible for parole until 2033. Murder charges against Lykken may be refiled eventually; the faked confession was not the only evidence against him. In March 2008, Black Crow pleaded guilty to two counts of perjury. He maintains that Lykken really had confessed the kidnappings and murders to him, and said he was unable to get the statements on tape and asked another person to repeat them.

Curiously, this is not the only time Black Crow has given evidence in a missing person case. In January 2007, Black Crow told investigators that one of his other cellmates, James Strahl, had admitted to killing Amanda Gallion, a teenager who disappeared from Wyoming in 1997 and was never found. Strahl was convicted of the 1998 murder of William O'Hare in September 2007. Black Crow testified against him, though he was not permitted to mention Gallion. Strahl's murder conviction was overturned due to Black Crow's false evidence in Lykken's case. In May 2010, Strahl pleaded no contest to grand theft and manslaughter in O'Hare's case and was sentenced to 35 years in prison. He also agreed to take a polygraph about his alleged involvement in Gallion's disappearance.

Authorities suspect foul play in Cheryl and Pamella's disappearances. They were both juniors at Beresford High School when they disappeared. Their cases remain unsolved.

Above: Lykken, circa 2008