William Labov — American Writer born on December 04, 1927,

William Labov is an American linguist, widely regarded as the founder of the discipline of variationist sociolinguistics. He has been described as "an enormously original and influential figure who has created much of the methodology" of sociolinguistics. He is employed as a professor in the linguistics department of the University of Pennsylvania, and pursues research in sociolinguistics, language change, and dialectology. He semi-retired at the end of spring 2014... (wikipedia)

We focus upon pairs of words very often which are the same in some areas and different in other areas.
But unlike European countries, America has never finished a map of the United States, only the eastern United States is covered and a few spots here and there.
This African American Vernacular English shares most of its grammar and vocabulary with other dialects of English. But it is distinct in many ways, and it is more different from standard English than any other dialect spoken in continental North America.
And instead of getting a pepper-and-salt effect, we find very clear and sharp divisions between the dialects of the United States, which are getting more different from each other as time goes on.
An important aspect of the current situation is the strong social reaction against suggestions that the home language of African American children be used in the first steps of learning to read and write.