“Legacy: Rocking the Nation (RTN), 30 Years of Creativity” takes a historic look at the origins of a cultural collective manifesting the four elements of hip-hop. The exhibition brings together visual art, photographic archives, black books as journaling and communication, music dance and words.    Formed in 1989, Rocking the Nation (RTN) originated as one of L.A.’s only all-black graffiti crews. With a strong focus on community building and education, the crew used the medium to unite disenfranchised youth and to…