Around the turn of the millenium (is that a phrase?), Japan's idol card industry was really just getting underway. Sure, (not always authorized) bromides could be found of the hottest J-Pop performers, and non-sport sets were being issued, but it's around 1998 that the first pure idol card sets were issued. I should mention that this is based on my own card-hunting experience, and there certainly could be earlier gravure idol sets out there. Instead of single models getting entire sets, many of the releases around this time were collections of girls. And around that time, a lot of race queen sets were produced.
The Japanese wikipedia article for gravure idols identifies 2000 as the beginning of the idol trading card industry, and this is when race queen cards began to be sold as well. I recently picked up a random lot of race queen cards at Nakano Broadway, and below is a sampling.
That's it for today! I should be back on baseball tomorrow.