The whole section around DC is..questionable. PG, Fairfax, and Loudoun counties are all in the Tidewater group that extends down to the NC triangle. Meanwhile Montgomery County, which is right over the Potomoc from Fairfax/Loudoun, is in a separate group that's shared with Philadelphia and Ohio? MoCo, Fairfax, and Loudoun are all incredibly similar both culturally and economically (i.e. wealthy DC suburbanites) and should either all be in the Tidewater category or in some separate "Capital Area" nation.