The blues is one of America's greatest musical treasures. A roots music form that evolved out of African-American work songs, field hollers, spirituals, and country string ballads more than a century ago, the blues is the foundation of virtually every major American music form born in the 20th century, including jazz, rhythm and blues, rock and roll, and hip-hop. As profound as the blues has been to the national music experience, it has only occasionally entered the American classroom, mostly through individual teachers who were committed blues fans and who created their own methods to integrate the music into curricula. Read the essays What is the Blues? and Understanding the 12-Bar Blues.