Geographically, dialects are the result of settlement history. Dialect development can be understood to some extent in relation to topography: where populations can communicate easily, dialectal differences develop more slowly than where they lose immediate (or all) contact. An effective method of studying such matters is the science of linguistic geography. Individual features (sounds, words, grammatical forms, etc.) can be displayed on maps showing where one or another feature prevails in use and where competing forms are found. Lines on a dialect map outline the area within which any form is regularly used (see image below). The type of language one speaks (a social dialect or sociolect) depends on community, family background, occupation, degree of education, and the like. Where a standard form has become established, the tendency is to consider it ‘right’ and to denigrate other varieties, whose only fault may be that they are out of style in the mainstream of a language. Distinctive dialects are most fully preserved in isolated areas (along sea coasts, on islands, in mountain areas) where they are little influenced by outsiders and the population is relatively self-sustaining. The dialects of large cities, however, run the social gamut of the language, with outside features being brought in and new features being created more or less continuously.
Traditionally, dialectologists have listed three dialect groups in the United States: Northern, Midland, and Southern; although some scholars prefer a two-way classification of simply Northern and Southern, and one may also find significant difference on the boundaries of each area.
The New England Dialects
These dialects are non-rhotic: dropping r's before consonants and at the end of words. This area is further subdivided into Eastern New England, including Boston and much of Maine, where O and AU shift into an intermediate vowel so that cot and caught are merged. Transitional between Eastern New England and New York, Western New England is less well defined. Providence retains R-dropping, but does not merge O and AU.
The New York Dialects
New York City has a rather anomalous linguistic situation, in that its local dialect was not reproduced further westward and therefore cannot be fit into any larger regional grouping such as New England or the Midland. Like New England, the dialect is R-dropping; other features are more generally common to the Northeastern seaboard. The Hudson Valley dialect of Albany, though R-preserving, is nevertheless close enough to New York City's to be grouped with it: both of them shared a Dutch linguistic substratum which is now only vestigial.
The Great Lakes Dialects
Among all the dialect regions, the Great Lakes region is perhaps the most homogenous, since the major cities in this area (Syracuse, Rochester, Buffalo, Cleveland, Detroit, Chicago, Milwaukee) are simultaneously undergoing a chain shift known as the Northern Cities Shift, with a rotation of the short vowels so that they may be heard as members of another phoneme by listeners from another dialect area with consequent confusion of meanings: Ann as Ian, bit as bet, bet as bat or but, lunch as launch, talk as tuck , locks as lax. This area is fully R-preserving, even though the earliest settlers of this area were primarily New Englanders. At present New England influence is evident only in the lexicon.
The Upper Midwest Dialects
This area is characterized mainly by a conservative vowel scheme, where the long vowels (often attributed to Scandinavian influence) have remained purely monophthongal, exemplified in the widely known long O in the name Minnesota. Along the northern border are found Canadianisms such as the centralized long I in fuyr (fire) and the centralized ow "uh-oo" in : ouwt (out).
The Midland Dialects
Midland dialects retain R in all positions, and long I is not flattened (monophthongized) as uniformly as in the South, but the Midland is otherwise not very easy to describe as a whole, since each of the Midland cities: Philadelphia, Pittsburgh, Columbus, Cincinnati, Indianapolis, St. Louis, Kansas City, has its own local character. More southerly Midland cities have a typically Southern fronted nucleus in ow, e.g. aout (out); more northerly Midland cities tend not to.
The Western Dialects
Western phonology has only recently begun to diverge, primarily with the merger of AU into the short O class: e.g. cot for both caught and cot, and the fronting of the long U class, e.g. "ih-oo" in words such as two. Otherwise it appears that the Western dialects were formed primarily from a Midland base, since both groups are similarly conservative in their phonology; in fact it was certainly Midland and Western dialects which were so often lumped together under the catch-all phrase "General American". Westward migration has also carried typically Northern features into the Pacific Northwest, and Southern features into the Southwest: both phonology and lexicon have been affected.
Regional dialects are examined by their disposition geographically, although the varieties of English can also be determined by other factors that shape usage, such as age, ethnicity, gender, and social class. Therefore, the inclination of change within the pronunciation of the English language is inevitable. In time, the possibility of transitioning speech is certain and the basis of the English language becomes more distorted and even less unified. Among the differences between dialects are variances in perceived charisma and identity to the national region. Dialect transition, evolution, and crossover are all dependent upon community stability and other outside influence. Differences in enunciation, inflection, and speech amongst Americans act to preservce the distinct and variant cultural identities.
Bibliography
"North American English regional phonology -." Wikipedia, the free encyclopedia. 22 Feb. 2009 <http://en.wikipedia.org/wiki/North_American_Regional_Phonology>.
MacNeil, Robert, and William Cran. Do You Speak American? United States: Nan A. Talese, 2005.
TOM McARTHUR. "DIALECT." Concise Oxford Companion to the English Language. 1998. Encyclopedia.com. 21 Feb. 2009 <http://www.encyclopedia.com>.