First punk gig was a triple bill with Gang Green, Negative FX, and Bad Brains (1982, I think) at a now defunct venue in Boston, MA called Mr. Mcnasty's Pub. A third of the crowd was slam-dancing up front in the mosh pit while the other two thirds of the crowd stood back around the bar area and watched the show from a safe distance.
There was an empty area between the slam dancers and the onlookers, sort of like a no man's land where no one ventured into. Lots of bruises, fat lips & bloody noses coming out of the mosh pit that day.