Jimmie Rodgers and the Carter Family are widely considered to be important early country musicians. Their songs were first captured at a historic recording session in Bristol, Tennessee, on August 1, 1927, where Ralph Peer was the talent scout and sound recordist. A scene in the movie O Brother, Where Art Thou? depicts a similar occurrence in the same timeframe. Rodgers fused hillbilly country, gospel, jazz, blues, pop, cowboy, and folk, and many of his best songs were his compositions, including "Blue Yodel", which sold over a million records and established Rodgers as the premier singer of early country music. Beginning in 1927, and for the next 17 years, the Carters recorded some 300 old-time ballads, traditional tunes, country songs and gospel hymns, all representative of America's southeastern folklore and heritage.
By the end of World War II, "mountaineer" string band music known as bluegrass had emerged when Bill Monroe joined with Lester Flatt and Earl Scruggs, introduced by Roy Acuff at the Grand Ole Opry. That was the ordination of bluegrass music and how Bill Monroe became to be known as the "Father of Country Music." Gospel music, too, remained a popular component of bluegrass and other sorts of country music. Red Foley, the biggest country star following World War II, had one of the first million-selling gospel hits ("Peace in the Valley") and also sang boogie, blues and rockabilly. In the post-war period, country music was called "folk" in the trades, and "hillbilly" within the industry. In 1944, The Billboard replaced the term "hillbilly" with "folk songs and blues," and switched to "country" or "country and Western" in 1949. https://www.youtube.com/watch?v=hyNAvdnZ5Ec