Blues became a part of American popular music in the 1920s, when classic female blues singers like Bessie Smith grew popular. At the same time, record companies launched the field of race music, which was mostly blues targeted at African American audiences. The most famous of these acts went on to inspire much of the later popular development of the blues and blues-derived genres, including the legendary delta blues musician Robert Johnson and Piedmont blues musician Blind Willie McTell. By the end of the 1940s, however, pure blues was only a minor part of popular music, having been subsumed by offshoots like rhythm & blues and the nascent rock and roll style. Some styles of electric, piano-driven blues, like boogie-woogie, retained a large audience. A bluesy style of gospel also became popular in mainstream America in the 1950s, led by singer Mahalia Jackson. The blues genre experienced major revivals in the 1950s with Chicago blues musicians such as Muddy Waters and Little Walter, as well as in the 1960s in the British Invasion and American folk music revival when country blues musicians like Mississippi John Hurt and Reverend Gary Davis were rediscovered. The seminal blues musicians of these periods had tremendous influence on rock musicians such as Chuck Berry in the 1950s, as well as on the British blues and blues rock scenes of the 1960s and 1970s, including Eric Clapton in Britain and Johnny Winter in Texas.