A region in America from Canada to Georgia. Usually taken to mean the Appalachian Mountains and home of Appalachian music.
Because of isolation of the area in the past, the culture is well preserved of the settlers who stopped there (Scottish, Irish, German and English mainly). There was also a French influence which migrated North from Louisiana.
A gap in the Appalachian Mountains is an important focus for Folk - The Cumberland Gap. It was through here that settlers found Kentucky which really does have blue grass.
Mostly the music and songs are from the settlers' home traditions and have evolved in the best folk tradition. Some have evolved so much that it is hard to recognise them and they have migrated back to their country of origin with a different title. (e.g. Virginia Reel / Sir Roger de Coverley).
Appalachia is also well known for old-time music.