Speaking as a Texan, it really amuses me (in an "isn't that cute" way) to imagine arguing over whether or not a county is in southern Maryland. Maryland is small enough you could probably throw a Nationals fan from one end to the other. "Southern Maryland" is probably defined as "the distance that a Southern Marylander would drive before feeling adventurous and/or out of place."
Just to boost my superiority complex, the Texas panhandle could fit two Marylands with a thousand square miles to spare.