IN THE 1970s a new African American and Afro-Caribbean youth culture began to take shape in one of the five boroughs of New York City known as the Bronx. Eventually this youth culture would come to be called hip hop, but at the time, even though it had no name, it could be seen. A new type of graffiti covering the sides of subway cars was the most visible evidence of its existence. Graffiti itself was nothing new; for years individuals had given themselves names or "tags" and written them on subway cars and buildings across the city. However, by the mid-1970s, graffiti had evolved from simple tagging into an art form. Artists no longer merely tagged subway cars, they now painted complex multicolored murals that sometimes covered entire subway trains. This elaborate graffiti was one of...