You forgot Maryland and Delaware.
Those are Mid-Atlantic.
No, look at the Census. They consider Maryland and Delaware to be part of the South Atlantic. (Of course, back when the census was first taken Maryland and Delaware were southern, but now they are only part of the South Atlantic for consistency.
OP also forgot West Virginia.
I'm familiar with those boundaries, but it'd be effectively pointless to include MD & DE - as has already been mentioned - and WV doesn't even border the Atlantic, so junk state. It's also worth pointing out that "Mid-Atlantic" in politics includes some states across those boundaries. It's comparable to discussing "Central America" in a conversation where the continents of North and South America are more formally recognized.