Promoted self-empowerment, "Don't Be A Dropout"
First, he was the "godfather" foremost pioneer of soul music. In the 50s and 60s and 70s, he and his bands helped to craft a louder and more disciplined sound that every other soul band modeled themselves after.
And he had an important role in Civil Rights movement as well. Not only did he sing songs inspiring the African-American community to empower themselves, but his concert in Boston in 1968 is credited with directly preventing a riot.
Not bad, eh?