Kiefer was 44 years old when she was last seen on March 22, 1994, troopers said. She was in bed when her husband woke up and went to take a shower, but was nowhere to be found when he returned, according to the Charley Project.
The family car was missing, as was the medicine she took daily for fibromyalgia and chronic fatigue.
The vehicle was later found abandoned in Bethlehem's Saucon Park, some four miles from her South Hoffert Street home, according to a 2001 report in the Allentown Morning Call. No evidence of foul play was discovered at the scene.
Her husband police they had had no marital issues and said her illnesses had kept her homebound for over a year before she vanished.
In 1995, her former neighbor Brian Steckel claimed he had sexually assaulted and murdered Kiefer, the Morning Call reported. Steckel was being held on death row in Delaware for the murder of a 29-year-old woman months after Kiefer's disappearance, and police later determined his confession was a lie.
Kiefer was declared legally dead in 2001, and Steckel was executed in 2005.
Anyone with information on her case is asked to call Pennsylvania State Police at 1-800-472-8477 or submit a tip online.
Click here to read the Morning Call's 2001 coverage.
Click here to follow Daily Voice Allentown and receive free news updates.