With the mass migration of blacks from the southern United States to the northern, midwestern, and western states, the blues-based music of the south began to spread widely with the migration to other parts of the country. Blues became popular as black professional music in the 1920s, jazz developed in black urban communities during the same period, black gospel music became widely popular among blacks in the 1930s, R&B emerged in the 1940s, country music began to gain prominence in the 1950s, and rock and roll music took off in the 1960s, followed by the popularity of soul and funk. Population migration brought about cultural exchange: different musical cultures collided and exchanged with each other, opening up the possibility of a nationwide market for specialty music.