In the 24 years since the first publication of the Billboard Hot Rap Singles Top 30 Chart, rap/hip-hop has grown by leaps and bounds in both terms of widespread acceptance and (seemingly) unstoppable global popularity. Upon publication back in mid-June of 1990, while popular enough to deem its own weekly chart, hip-hop was still somewhat marginalized and was far from the mainstream cultural force it is today. However, while examining the contrast between radio/sales charting hip-hop in 1990 and 2014, there are many notable differences. For starters, hip-hop was still largely labeled or referred to as "rap" back then, which is somewhat ironic since popular "hip-hop" today is technically more "rap" than it was back at the beginning of the nineties.
From eyeballing this June 1990 chart that was compiled from a national sample of both retail and one-stop sales, it's evident that commercially popular hip-hop appeared to be a lot more adventurous and much more diverse in style both production-wise and lyrically. Also notable is how major labels did not dominate the bulk of rap sales. It was pretty much evenly split between indies and majors, although many of those same independent labels would in time make deals with the majors. Another notable business factor was that record labels (indie or major) could still be very profitable ventures since 1990 was a time when people still bought records and tapes to hear music. There was no illegal free downloading/file-sharing of music and the only threat to labels was illegally dubbed bootleg cassette copies of their releases. Hence labels had more money to spend on promotions of their artists.
Women hip-hop artists, whom to this day have never gained equality in their genre, were still in the minority back in June 1990 with only five out of this top 30 chart being female acts. These five included three groups - something much rarer today when female rappers tend to be solo acts - and included Hammer proteges Oaktown's 3-5-7, Def Dames (whose "Set It Off" heavily sampled Strafe's 1984 club/radio hit of the same name and who should not be confused with the Euro girl group who came a little later), and early career Jermaine Dupri-discovered rap/r&b trio Silk Tymes Leather. The other female chart entries were Icey Jaye ("It's A Girl Thing"), and Queen Latifah in a duet with David Bowie for "Fame 90."