Under current Maryland law there are two types of divorces allowed, "Absolute divorce" and "Limited divorce". In most cases, the law requires that both parties live separately for a period of 12 months before an absolute divorce is granted.
There is no such thing as a legal separation in Maryland. However, the law recognizes that sometimes spouses want to live apart from each other yet have certain financial decisions which first need to be immediately addressed and can't wait for 12 months. For example, a determination may need to be made regarding which spouse is responsible for the monthly payments of a shared vehicle.
Maryland also recognizes that there are some situations in which an absolute divorce needs to be granted immediately. Situations involving things like adultery, cruelty of treatment and excessively vicious conduct can be grounds for the court to step in and dissolve the marriage right away. Parties engaged in an absolute divorce are permitted to remarry after it is finalized.
It is not necessary for both parties to be separated before either spouse can file for divorce, yet most grounds for divorce require spouses to maintain separate residences for a period of time.
If you and your spouse have committed to divorcing each other, and you are still on fairly good terms, then it may be in your best interests to get together with a mediator and work out a separation agreement. Although a separation agreement does not have to be filed with the court, it's a contract agreed upon by both parties that often becomes part of the final divorce agreement. A good separation agreement will work out things such as child custody, child support, distribution of assets and property and more.
Source: mdcourts.gov, "Maryland Courts - Legal Help Family Issues" Aug. 21, 2014