The towel was found with the baby's tiny body in a wooded area roughly 10 feet from the shoulder of Southeast North Bend Way, according to Cindi West with the King County Sheriff's Office.
Detectives said the towel is a full-size faded black bath towel with multiple color square patterns on one side and rectangles on the other side. The towel is a Target brand, Home Collection.
The newborn's body was found along this stretch of road near Snoqualmie.
Anyone who recognizes the towel or has information about the newborn is asked to call the King County Sheriff's Office at (206) 296-3311 or call Crime Stoppers at 1-800-222-TIPS (8477) to remain anonymous and be eligible for a reward of up to $1,000.
The location where the baby was found, near the Kimble Creek Bridge, is roughly a mile away from the Snoqualmie Casino.
West said the baby was "full term" with its umbilical cord still attached. She did not say if the baby was a boy or a girl.
"We're looking for somebody to help us identify who this baby belonged to," West said. "Somebody has got to know somebody who was pregnant recently that is suddenly not pregnant anymore, and there no baby is sight."