LL Cool J backed out of Philadelphia's July 4th concert, refusing to cross a picket line amid a city workers' strike.

(Photo credit: BET.com) On August 11, 1973, an 18-year-old, Jamaican-American DJ who went by the name of Kool Herc threw a back-to-school jam at 1520 Sedgwick Avenue in the Bronx, New York. During his ...