The Borough of Fenwick, Old Saybrook, Connecticut.
There are hundreds of elitist, WASPy, old private communities like this scattered around the Northeast. Many operate as, or like, private clubs and some are more informal. I know about a lot of them, but have not been to many of them. They tend to be so discreet that you would not know about them.
Blooming Grove is great with thousands of acres, several streams and lakes and great old houses, but you have to be related to one of the founders to have a house there.
We all live in different realities.