Twisterdog, here is a short version, from Reader's Digest "Success With Words, A Guide To The English Language",1983.

"There are two major divisions of dialect, sociolinguistic and linguistic geography. The first studies the language varieties of various social groups, the second studies the language variety of a particular region of a country.

"In the US the larger divisions of regional dialect are Northern, North Midland, South Midland, Southern, and Western. These are further divided into Hudson Valley, Inland Northern, New England, New York City, Pacific Northwest, Pacific Southwest, Rocky Mountain, Southwestern, Virginia Piedmont, Coastal Southern, Gulf Southern, and South Midland."

There are lots of smaller divisions, too; in NYC it's easy to tell who is from the Bronx or Joisey. Everyone can tell a Minnesota accent from a Chicago accent. etc.

Well, I think I'll go fix a gorilla cheese sanwhich!