Appalachian English is a common name for the Southern Midland dialect of American English. This dialect is spoken in Northeastern Georgia , Northwestern South Carolina, Southern West Virginia, Southwestern Virginia, Southern Ohio, Eastern Kentucky, the Upper Potomac and Shenandoah Valleys of Virginia and West Virginia, Western Maryland, East Tennessee, and Western North Carolina as well as northeastern Alabama. It is a dialect distinct from Southern American English, and it has more in common with the Northern Midland dialect of Pennsylvania and Northern West Virginia than the non-rhotic Southern dialect. While most of this area lies within Appalachia as defined by the Appalachian Regional Commission, Appalachian English is not the dialect of the entire region the Commission defines as Appalachia.
The dialect is rhotic and characterized by distinct phonology, morphology, syntax, and lexicon. It is mostly oral but can also be found in writing. Detractors of the dialect both within and outside of the speaking area cite laziness or indifference in learning standard forms as the reasons for its existence. However, the areas where Appalachian English is spoken were settled in the 18th century, and many of the characteristics of the dialect predate the standardization of American English and continue to be passed on orally.
English speakers who settled the area came mostly from West Anglia, the Scottish Lowlands, Wales, Ireland, and Scotland via Northern Ireland in the middle 18th and early 19th centuries, and their speech forms the basis of the dialect. Along with German immigrants, these groups populated an area which is still largely homogeneous culturally.
Many speakers assert that those who came to Appalachia from the Scottish Borders by way of Northern Ireland, the Scots-Irish or Ulster Scots, had the greatest role in shaping modern Appalachian English, and this is supported by a large number of extant vocabulary used in the least urbanized, and therefore more linguistically conservative, areas of the Appalachians.
Speakers of Appalachian English have no trouble understanding standard English, but even native speakers of other dialects can find it somewhat impenetrable (compare the similar situation of Glaswegian and London English), and foreigners may have some trouble understanding it, while others may find it easier to comprehend. Standard forms are taught in schools, unfortunately with the erroneously implicit assumption that the Appalachian dialect is somehow inferior to Standard American English.
The characteristic syntax and morphology of Appalachian English gives way to more standard forms in schools, public speaking venues, and courts of law, but the phonology is likely to remain the same.

Phonology

Conjugation of the verb "to be"
Sometimes the past participle of a strong verb such as "do" is used in place of the past tense. For example, "I done it already" instead of "I did it already" or in the case of the verb "see," "I seen" instead of "I saw."
"Went" is often used instead of "gone" as the past participle of the verb "to go." She had went to Ashland. Less frequently, "gone" is used as the simple past tense. I gone down to the meeting, but wasn't nobody there.
"Done" is used with the past tense (or a past participle commonly used as a past tense, such as "gone") to express action just completed, as in, "I done went/gone to the store".
Some English strong verbs are occasionally conjugated as weak verbs in Appalachian English, i.e. "knowed," and "seed." Most speakers of Appalachian English do not use these forms, however, as they indicate the lowest level of social prestige.
The construction "don't...no" is used with transitive verbs to indicate the negative, i.e. "He don't know no better." This is commonly referred to as the double negative, and is either negative or emphatically negative, never positive. "None" is often used in place of "any," as in "I don't have none."
Verb forms for the verb "to lay" are used instead of forms of the verb "to lie." For example, "Lay down and hush."
Often, got is used in place of have. "If they ain't got it, you don't need it."
Participles found in present tense progressive aspect verb forms often have a vowel prefix commonly written with an "a" followed by a hyphen, and this is pronounced as a schwa sound. An example is "I'm a-goin' now." Cf. the composite present of Scottish Gaelic, as in Tha mi a-smochach, or "I'm smoking."
"Might could" is sometimes used where a speaker of standard English would say, "could maybe.". Cf. Scots and Ulster Scots "micht could".
"Feet" - when speaking about measurement - is often replaced by the singular, "foot". For example" "That stick is 3 foot", or "We need 6 foot of drywall".
The future perfect is all but nonexistent.

Other verb forms
"Them" is sometimes used in place of "those" as a demonstrative in both nominative and oblique constructions. Examples are "Them are the pants I want" and "Give me some of them crackers."
Oblique forms of the personal pronouns are used as nominative when more than one is used (cf. French moi et toi). For example, "Me and him are real good buddies" is said instead of "He and I are really good friends."
Accusative case personal pronouns are used as reflexives in situations that, in American English, do not typically demand them (e.g., "I'm gonna get me a haircut"). The -self/-selves forms are used almost exclusively as emphatics, and then often in non-standard forms (e.g., "the preacher hisself").
Second person pronouns are often retained as subjects in imperative sentences (e.g., "You go an' get you a cookie").

Sample vocabulary
O'Grady, William, Dobrovolsky, Michael, and Aronoff, Mark. Contemporary Linguistics: An Introduction. Second Edition. New York: St. Martin's press, 1993.
D.A.R.E., The Dictionary of American Regional English