Nantucket is in Massachusetts. I once knew a man from there.
I think you are thinking of Newport, RI.
Martha’s Vineyard, MA is also very preppy.
I’m sure there are plenty.
I think of LA as more fashion conscious in a sort of flashy, showy sort of way. Preppy clothes are generally characterized by being simple, well made, timeless, usually without overt branding. Things like Brooks Brothers suits, peacoats, Burberry scarves, nautical-looking sweaters. Stuff like that.
When people in my company have to go to northern Italy for conferences, one of the first things they say is “Dress really, really well.” And we’re a professional outfit. Dressing well is considered basic manners in Italy, far more so than North Americans are used to anymore.
Philly is so beyond dress down casual (in some nabes): Shorts, work boots (not necessarily Tims), t-shirt with a Phillies jersey over it, ball cap on backwards. Not my look, but mostly because of the jersey and hat.
It’s a town filled with old guys wearing boat shoes and shorts pulled up to their nipples, legislators wearing business attire (which, while formal, isn’t particularly preppy,) and shoeless philosophy students. The midshipmen have a bit of a preppy look to them, but they don’t come out of the Academy much.
Then again, I haven’t lived there since 2004, so things might have changed. I never would have imagined that much, though.
The last time I walked around Ananpolis I saw almost nothing but cord shorts, polo shirts, and deck shoes. There was an astounding amount of Lily Pulitzer, and navy blazer/oxford shirt combos were predominant at dinner.