Actually, it's pretty fair to presume that they were pioneers of rave. True they weren't big at the same time as the Happy Mondays, Primal Scream, or Westbam, but they were releasing tracks as early as '91:
They were around from the beginning but they had a lot of contemporaries too. Like I said, I'm not an expert but rave culture arguably got going in 89 with the rising popularity of house and then techno (this still sounds fresh from 89 http://www.youtube.com/watch?v=6musPMSe24Q)
Around 90 and 91 it moved to a focus on more hardcore techno and breakbeat. Mr Kirk's Nightmare by 4Hero was around 1990, which sounds quite primitive now but quickly spawned records like those produced by NRG, Prodigy and G Double E. Prodigy were part of a much wider scene but had the talent and music to go mainstream.
Apologies to anyone if I've got this wrong. I was about 10 back then but I have plenty of friends who lived through it (and indeed were DJs back then!) so I've picked up a lot.
No worries. I was actually producing my first underground events back in '90 in San Diego. Obviously I wasn't in the middle of the makers, but I was moderately aware of what was going on.
We didn't really have "techno" & "breakbeat" until '91, but there were hints of it. Meat Beat Manifesto were doing industrial breaks using the drum samples that came into popularity later on. I don't have time to go into history, but there's also the US techno influences that came into play in '90.
I can share one story: back in '89 hanging on in a tiny record shop in San Diego known for industrial, new beat, and dance music. They got in some domestic imports. We gave them a listen and thought "these are really great, but where are the lyrics?"
It would have been great to see those early events in San Diego. I'm very envious! One thing we did have back in the early 90s here in Manchester was a great radio station called Sunset (it quickly became a commercial mainstream station, alas). Some shows can be found here:
http://durftal.com/music/bonus1/index.html
http://en.wikipedia.org/wiki/The_Prodigy
And unlike their predecessors, their production is far more in line with the rave sound and iconography that any other group of that era.