Delta blues

The Delta blues is one of the earliest styles of blues music. It originated in the Mississippi Delta, a region of the United States that stretches from Memphis, Tennessee in the north to Vicksburg, Mississippi in the south, the Mississippi River on the west to the Yazoo River on the east. The Mississippi Delta area is famous both for its fertile soil and its extreme poverty. Guitar and harmonica are the dominant instruments used. The vocal styles range from introspective and soulful to passionate and fiery.

Source : http://en.wikipedia.org/wiki/Delta_blues