‘Prewar blues’ charts the development of blues music up until 1939. Whilst record companies found ethnic records generally profitable, they assumed that African Americans liked white music. That is until Mamie Smith recorded Crazy Blues, and spawned a craze for ‘blues queens’. The work of Fiddlin' John Carson and Blind Lemon Jefferson also showed record executives that people in the south still wanted local music recordings despite the availability of big band. Country blues centred around Texas, the Piedmont, and the Mississippi delta. The migration of African Americans to cities, coupled with the Great Depression and prohibition, gave rise to the ‘hipper’ urban blues.