Recorded blues and country can be found from as far back as the 1920s, when the popular record industry developed and created marketing categories called "race music" and "hillbilly music" to sell music by blacks for blacks and by whites for whites respectively.
Hereof, why is it called the blues?
The name of this great American music probably originated with the 17th-century English expression "the blue devils," for the intense visual hallucinations that can accompany severe alcohol withdrawal. Shortened over time to "the blues," it came to mean a state of agitation or depression.
When did blues music become popular?
In the 1920s, the blues became a major element of African American and American popular music, reaching white audiences via Handy's arrangements and the classic female blues performers. The blues evolved from informal performances in bars to entertainment in theaters.