The true identity of this artist is NOT known for certain.
The prevailing theory (since at least 1969) is that his true identity is one Joe Holmes (based on research by Gayle Dean Wardlow).
However, since 2011, blues historian Alex van der Tuuk undertook a more thorough research into King Solomon Hill's identity. While he managed to unearth more information on Joe Holmes (as part of this investigation), there remains no conclusive evidence as to who this man actually is (refer to the book contained in Various - The Rise And Fall Of Paramount Records 1928-1932, Volume 2 for more detail).
The photograph (left) is of Joe Holmes, who:
Born: 1897, McComb, Mississippi, USA
Died: 1940 or 1949, Sibley, Louisiana, USA
As of 2011, he is known to have made 8 recordings (sides):
Whoopee Blues (Take 1)
Whoopee Blues (Take 2)
Down on my Bended Knee (Take 1)
Down on my Bended Knee (Take 2)
The Gone Dead Train
Tell me Baby
My Buddy Blind Papa Lemon
Times Has Done Got Hard