I've never considered Maryland to be part of the Confederacy below the Mason-Dixon line back in those days; nor the Northern portions of Virginia.
Admittedly, I'm just spouting without doing further research. ....My opinion is probably driven by the liberalism that exists in those areas.
Do more research. Maryland was very much a Southern State, but was occupied by northern State Militias before Virginia voted on secession. Had that vote come sooner, the conflict would have been vastly different.
Keep in mind, the words of the Maryland State Song "Avenge the patriotic gore/which flecked the streets of Baltimore" referred to riots in which the locals threw bricks and stones at the invading northern troops. (The State song Maryland, My Maryland was written by an expatriate in Louisiana during the war), and Maryland had regiments in the Confederate Army.
Unfortunately, the invading Yankees carpetbagged Maryland, too, and the liberal/criminal government mindset has plagued the State since.