My mother was born and raised in New York City. She claims she can tell what block somebody grew up on based on their accent. I don’t have her Kreskin-like powers. (e.g. knowledge of when the fridge door opens when she isn’t in the room, knowing to the penny how much groceries will cost with tax even! If you throw miscellaneous things in the cart when she isn’t looking, etc.) I was wondering if accents really are that pronounced in NYC that her claim is valid? Is this just a New York thing, can people do the same in Chicago? Boston? Montreal isn’t the same that way; you can tell what city/ville a person is from, but neighbourhoods now are a horse of a different colour, they all start to blend after a while…
It depends to some degree on your mother’s generation, but yes, in general there is a lot of diversification in NYC that distinguishes people on the basis of neighborhood, ethnicity, socioeconomics, and religion. Those neighborhoods have been there for a long time in American terms, and for a long time there was very little mobility within the city. So your mom probably can tell quite a lot from an accent. But it’s a very complex topic. Have a look at the Telsur Project at Penn, that will give you an idea. There are links to work on NYC in particular, as well.
People have this idea that language is becoming more homogenized due to the media, but in fact the exact opposite is true. Language varieties over space (dialects, if you prefer) are becoming more distinct from one another in the United States. If you’re really interested and want to see a lot of maps, here’s a pdf of chapter eleven of the Phonological Atlas of the United States. Be warned that the discussion is highly technical and the maps take some studying, but they will give you an idea of the great range of language diversity in the U.S.
Oh and: there is a very, very distinct Chicago accent. A number of them, as a matter of fact.