I think Whitman started a trend in literature of reversing the dichotomy between the privileged and lower classes, or at least respecting the lower classes (the prostitutes, the drunks, the beggars) enough to represent them in his writing instead of ignoring them for more genteel subjects. Ginsberg followed suit in"Howl"- the crazy and the disenfranchised and the counter-culture are the revered "best minds." Dylan did something similar in his songwriting, probably due mostly to Ginsberg and Guthrie, singing through the voice of the poor and the ignored (Hattie Carole, Blowin in the Wind, Tombstone Blues, etc). That's why I think so many modern folkish songwriters write songs like Steve's "Simple Man etc" or Patty Griffin's "Chief," which focus on the same kind of underrepresented and generally disrespected characters Whitman tried to represent in his writing.
That is all.