What was Langston Hughes’ poetic contribution?

I would say that Hughes' greatest and largest contribution
to poetry is to bring voice to those who were silenced by the cultural majority. 
Hughes' poetry is especially powerful because it speaks for people of color in a nation
and in a time where they were not heard.  Yet, I think that Hughes' work can be
extrapolated to anyone who is the victim of being silenced, or anyone who seeks to be
heard.  So many of his poems seek to bring voices and narratives from margin to center. 
This becomes a very large portion of Hughes' writing and his motivation.  I think that
this becomes on of his best contributions to the discourse of the time and makes him
invaluable for all time.  In his work and his poetry in particular, there is a demand
for voices to be heard, for experiences to be acknowledged.  In this light, Hughes'
contributions are not only literary, but political and historical, as
well.