At what age can a child be left alone in the state of Maryland? 
Children under age 8 cannot be left home alone for any reason. Children age 8 or older can be left home alone for short periods of time, as long as a parent or other adult can be contacted. Short periods of time could be before or after school, not an entire day.  Parents must use their own discretion. Children under the age of 13 cannot babysit, even for brothers and/or sisters. A child age 13 can babysit, although the regulations do not specify for how long. For further information or consultation, or to report child or children left home alone either presently or on an ongoing basis, contact Child Protective Services.
https://www3.montgomerycountymd.gov/311/Solutions.aspx?SolutionId=1-NJRWV&AspxAutoDetectCookieSupport=1

Babysitting Safety