The Rainbow Family had one of their big gatherings up in northern NM back in about 97 or 98, up on the Carson NF. The gathering spot was right where I'd hoped we could put out elk camp in October. The last of them pulled out in early August and I walked over the area on a scouting trip. You could tell a lot of vehicles and people had been there from the way the grass was beaten down and the condition of the road, but there was no trash, no fire pits, and no other sign. A couple of months later, you could never tell that a few thousand people had camped there. I don't know if all their gatherings are as conscientious, but that particular event impressed me.
