Harvard police asked for the public's help in finding the young mother and her 5-month-old son after investigators said they were picked up by a man at the Harvard Diggins Library on Wednesday afternoon.
At the time, police said they believed the teenager left willingly and may have been heading to Kentucky.
Harvard police said the teen, her son, and 22-year-old Michael Walton surrendered to police unharmed early Friday morning in Cynthiana, Kentucky.
Walton has been charged with child abduction and is currently being held in Kentucky as he awaits extradition.