What is the history of folk music?

American folk music, also known as Americana, is a broad category of music including Native American music, Bluegrass, country music, gospel, old time music, jug bands, Appalachian folk, blues, Tejano and Cajun. The music is considered "American" because it is either native to the United States or there varied enough from its origins that it struck musicologists as something distinctly new; it is considered "roots music" because it served as the basis of music later developed in the United States, including rock and roll, rhythm and blues, and jazz.