Illinois law requires children to be 14 years old before being left alone; in Maryland, the minimum age is 8, while in Oregon, children must be 10 before being left home alone.Many States offer guidelines for parents that can assist them in determining when it’s.llinois law requires children to be 14 years old before being left alone; in Maryland, the minimum age is 8, while in Oregon, children must be 10 before being left home alone.Many States offer guidelines for parents that can assist them in determining when it’s.