In many states, a minor can petition the court to be emancipated, which allows them to enter into legal contracts and represent themselves as an adult. Minors who are married or join the military with parental consent become emancipated as well.
In Maryland, the only way for a minor to become emancipated is through one of these options (becoming married or joining the military with parental consent). Being emancipated makes you legally an adult, but it does not change your access to activities which have an age restriction, such as drinking alcohol or purchasing tobacco.
Even if a court petition of emancipation is not granted in Maryland, minors do have some rights, such as the ability in some circumstances to make their own medical decisions. In other states, a minor will have to show that they are able to care for themselves and pay for their own living expenses before being granted emancipation.
A Columbia, Maryland family law attorney can provide more information about emancipation.