First recollection of screenprinting was printing at my college Colgate University, helping a friend do a limited edition (about ten shirts) Mr. Natural (R. Crumb character) shirt that also said, "Keep on Truckin."
Until recently I had this shirt, it was a primitive print on shirt just a primitively tie-dyed.
We printed the shirts in the "Old Bio Building" which soon was at the time a rundown art space. The Olin Corporation had donated a new bio building and stipulated that Old Bio was to be torn down. The next t-shirt I remember working on was "Save Old Bio" shirts which I honestly cannot remember if we had stenciled or screenprinted. Activism so often does not succeed, but in this case we did start a campaign which did indeed save Old Bio and it stand until this day.
This was about 1971 and I think we hand cut the Mr. Natural stencil. I was helping my friend Peter Brown (now a PHD researcher in biology I think) because back in the day the water-based inks dried so fast you needed extra hands to keep moving or else the screen would permanently be clogged.