Generally, if you've voted in Maryland before, you don't need anything at all.

From the state website:

> Under the Help America Vote Act, certain voters must satisfy an identification requirement before voting for the first time in Maryland. A voter is subject to this new identification requirement if the voter:

> - Registered to vote by mail; and

> - Will be voting for the first time in Maryland.

> Because of the voter registration requirements effective January 1, 2006 (see above), most voters will satisfy the identification during the registration process. Generally, only the following voters will be subject to the identification requirement:

> - Those voters who do not have a driver's license, MVA ID card, or social security card and who submitted their voter registration applications by mail after January 1, 2006; and
> - Those voters who registered to vote by mail between January 1, 2003, and December 31, 2005, and have not yet voted for the first time.