much as Maryland and Delaware are profoundly southern.
Why?
Because they're culturally, demographically, and geographically Northeastern. I mean, c'mon Delaware is mostly a suburb of Philadelphia. And DC and Baltimore are literally defining components of the Northeast Corridor. The South begins somewhere well into Virginia.
There are plenty of metros which cross-cross geographic regions--Louisville crosses between the South and Midwest and NYC is in the Mid-Atlantic (or whatever you want to call NY/NJ/PA) and New England. Maryland, Delaware, DC, and Virginia can be part of the Acela corridor and still be Southern.
The thing is that Maryland and Delaware, in most functional respects, look like Southern states. They have large rural Black communities in non-montane areas, they have weak municipalities and strong counties, they have large swaths of Black suburbia, and they both have a history of rural Democratic support similar to the solid south.
Excluding the DC area, Maryland and Delaware both vote basically like downstate Virginia or North Carolina--Baltimore is an older southern city so it's a little unconventional, but it doesn't vote too differently from New Orleans if you exclude the areas also under DC influence. And of course the DC area itself is basically sui generis--if Nashville or Mobile were home to the federal government and bureaucracy, they would vote similarly and have a similarly placeless culture. However, in terms of urban structure and layout, DC is very Southern--it's often remarked that Prince George's County has its closest urban parallel to the majority Black and middle-class suburbia of metro Atlanta, and this isn't a coincidence.
Regional cultures in America have been blending, which makes it harder for people to recognize the southernness of MD, DE, and VA. Combined with the underlying sense of "Deep South=Southern", it results in such galaxy-brain takes such as "Virginia is no longer a southern state".
Southernization of the broader American national culture is a thing.
