I easily could have gone through every major and minor city, citing all of the of the self imposed/organized segregation of peoples ( The Irish & Italians in Boston, the Canadians in New Hampshire, the Chinese in San Francisco, various sections of different cities that segregated Christian from Jews, also segregating Catholics from Protestants, etc., etc., etc.! ), but kept it pretty simple.
FRmail for you....
You know your country well :)
There’s still some residual among the Italians and Irish in that area but I would assume not nearly as much anymore.