Bluegrass music is an American grass roots music influenced by Irish, Scottish and English traditional music. Bluegrass was inspired by the music of immigrants from the British Isles (particularly the Scots-Irish immigrants in Appalachia), as well as jazz and blues. Blue Moon of Kentucky is the official state bluegrass song. The bluegrass music genre is associated with the entire state, not just the bluegrass region.
Appalachia is a term used to describe a geographic region in the eastern United States that stretches from southern New York state to northern Alabama, Mississippi, and Georgia. Although part of the Appalachian Mountains extend through New England and into Canada, this area is not included in the accepted geographical definition of "Appalachia."
Over twenty million people live in Appalachia, an area roughly the size of the United Kingdom, covering mostly mountainous, often isolated areas from the border of Mississippi and Alabama in the south to Pennsylvania and New York in the north. Appalachia also includes parts of the states of Georgia, South Carolina, North Carolina, Tennessee, Virginia, Kentucky, Ohio, Maryland, and the entire state of West Virginia. The region contains few intermediate-sized cities, and only two large metropolitan areas are located entirely within the region - Pittsburgh, Pennsylvania, and Knoxville, Tennessee.
However, the expansive region served by the Appalachian Regional Commission incorporates some additional urban areas, including Birmingham, Alabama, the northern part of the Atlanta metropolitan area, western fringes of the Charlotte area, western fringes of the Piedmont Triad area, western fringes of the Washington metropolitan area and the eastern fringes of the Nashville metropolitan area.
(indented text is condensed and edited from Wikipedia.org: Bluegrass Music and Bluegrass Region, published under the GNU Free Documentation License).