I have to agree that historic preservation in New England is one of the region's best aspects (although it does have level of fervency in
some cases that can inhibit progress, but that's another conversation).
I do think the Mid-Atlantic is much more of a preservation hotspot that it often gets credit for.
Outside of the obvious larger (Philadelphia, New York, Baltimore, and DC) and or well-known hotspots (Alexandria, Lancaster, and Gettysburg) lesser-known gems like
Bellefonte, PA,
New Castle, DE, or
Frederick, MD are fantastic in this regard.
I do think Pennsylvania, in particular, has relatively large number of reasonably intact historic districts, even in post-industrial cities like
York and
Reading, where you might expect a LOT more urban renewal.
Even small, rural 'burgs like
Hamburg often have pretty historically intact/active business cores for their population size, which are so crucial for local communities.