Audrey Backeberg was 20 years old when she disappeared from her home in the small city of Reedsburg on 7 July 1962. In a statement, Sauk County Sheriff Chip Meister said Ms Backeberg's disappearance "was by her own choice and not the result of any criminal activity or foul play".

The sheriff said she was living outside Wisconsin, but did not provide any further details. According to Wisconsin Missing Persons Advocacy, a non-profit group, Ms Backeberg was married and had two children when she went missing.

The group said that days before she went missing, Ms Backeberg, now 82, had filed a criminal complaint against her husband, whom she had married at the age of 15, alleging he had beaten her and threatened to kill her. On the day she disappeared, she left home to pick up her pay cheque from the woollen mill where she worked.

The couple's 14-year-old babysitter told police she and Ms Backeberg then hitchhiked to Madison, Wisconsin's state capital, and from there caught a bus to Indianapolis, Indiana, about 300 miles (480km) away. The babysitter then became nervous and wanted to return home, but Ms Backeberg refused and was last seen walking away from the bus stop.

The Sauk County Sheriff's Office said investigators pursued numerous leads in the case but it had gone cold before a comprehensive review of old case files was carried out earlier this year.

The detective who solved the case, Isaac Hanson, told local news station WISN that an online ancestry account belonging to Ms Backeberg's sister was crucial in helping locate the missing woman.

Det Hanson said he contacted local sheriffs where Ms Backeberg now lives, and spoke to her on the phone for 45 minutes. "I think she just was removed and, you know, moved on from things and kind of did her own thing and led her life," he told WISN. "She sounded happy. Confident in her decision. No regrets." (BBC)