If indeed blues is a genre of folk music, it differs from other types of folk music in at least one significant aspect-songs in the other types of folk music have no known composers, but most if not all of blues songs have known composers or at least for early blues musicians who credit themselves as the composer of that piece.

Here's an interesting article that I found about W. C. Handy, who was called himself and was known as the Father of the Blues: http://www.perfessorbill.com/ragtime4b.shtml

Here's an excerpt of that article:

"Growing up in post-Civil War Alabama, the music of Black America and African heritage surrounded young Will Handy. His parents were well enough off to get him music lessons, and his first instrument was the cornet. In his late teens Handy started touring the South with various troupes and shows. According to him, it was in 1892 in Mississippi that he had his first exposure to Delta Blues. He eventually took over one of the groups he traveled with in 1896, and built up a repertoire of light classics, cakewalks, and early rags. Most of their travels were in the Mississippi Delta area through the early 1900's.

Although Handy called himself "the Father of the Blues," he did not invent the blues form. He was at least the third composer to use the term "blues" in a song title, preceded three weeks by Artie Matthews' arrangement of Baby Seals Blues. Handy's first blues piece was first put down in 1908 when he was commissioned to write a campaign song for the mayor of Memphis, Edward H. Crump. The song was published as Mr. Crump and went over well. When the blues was finally acknowledged as a publishable genre in 1912, Handy retooled the piece and published under the name Memphis Blues. This time it included "blue notes" (flatted thirds and sevenths) and a more definitive 12 bar blues section. The publication of this and other early pieces like the train oriented Yellow Dog Blues, started a veritable flood of blues-styled compositions...

In the 1930's when the playing jobs started to disappear, he wrote his autobiography, Father of the Blues. On a 1938 Ripley's Believe It Or Not radio program, Handy's role was lauded as not only the father, but the inventor of the blues. This incensed one of it's listeners, Ferdinand "Jelly Roll" Morton, who knew better. In a letter that was sent to Ripley and later read on the air, Morton made it clear that it was more likely that HE introduced the blues, not to mention, jazz, to the world, but stopped short of claiming invention rights. In truth, no one man invented the genre, but both certainly spread it throughout the world. While not the originator of the blues, Handy was certainly it's most effective spokesperson, and continued to promote the music form and push for its inclusion in the early 1900s American music vernacular."