From the Chesapeake Bay to the hills beyond Hagerstown there is climbing to be found in Maryland, although most of the climbing can be found in central Maryland.
Rock State Park, Carderrock, A-Rock, and other various climbing locations are generally small, short but have beautiful setting and fun moves. Finding a local that knows where the classics are is defintely the crux of Maryland climbing.
Indoors gyms are extremely common, generally huge, and well-kept.
Getting There
Maryland is a state, there are only 50, learn them know them, and even though the East coast states are small we have fierce devotion to our repective home states so don't say "oh! that is one of the small ones over by..." if you want to make friends.
For a better description of Maryland Climbing check out Indy's Climb Maryland book. Here is the link for amazon.com. http://www.amazon.com/Climb-Maryland-Mark-Indy-Kochte/dp/096>>>>> It is more thorough than any other guide. Maryland, when you actually go looking has a lot of climbable rock, you just need to get out there and find it.