http://rap.about.com/od/hiphop101/a/hiphoptimeline.htm

1973: DJ Kool Herc deejays his first block party (his sister's birthday) at 1520 Sedgwick Avenue, Bronx, NY. Herc would often buy two copies of a record and stretch the break parts by using two turntables and mixing in both records before the break ends. The Zulu Nation is officially formed by a student of Stevenson High school named Kevin Donovan. Donovan later changed his name to Afrika Bambaataa Aasim in honor of an ancient Zulu chief.

1974: After seeing DJ Kool Herc perform at block parties, Grandmaster Caz, Grandmaster Flash, and Afrika Bambaataa start playing at parties all over the Bronx neighborhoods. Around this time, DJ/MC/Crowd Pleaser Lovebug Starski starts referring to this culture as "hip-hop."