Technically, I didn't exactly know where it was. I just knew that STP racing stickers came from there.
Some enterprising 5th grader had figured out that if you simply knew where to ask, most marketing and promotions departments in companies that produced racing and performance products would simply mail you an adhesive logo. I'm sure the intention was for serious adults to stick these on toolboxes and garages to promote the sale of more product, but the companies didn't seem to care that the requests came in the form of hand written pencil letters that started "Dear Sir".
There were sheets of three hole punch notebook paper with hand written "addresses" that we would dutifully copy from one another with far away places in Michigan or Ohio. Some addresses worked and others were just dead ends.
The STP address always hit jackpot. Some were for products none of us knew anything about. What the heck was an oil filter? None of us knew but we knew you could trade a rare Fram for something you didn't have yet.
Some yielded multiple stickers per brown envelope, some a single but none were as treasured as the multicolored, shiny foiled fiery AC spark plug.
Most of the stickers were just collected in large brown envelopes and brought to school to be traded. Extras were stuck to bedroom closet doors or to bedposts, much to my fathers annoyance.