It was first observed in the US during
October 1984. The observance was thought up by Gerry Durnell from
Santa Claus, Indiana and the founder of Pizza Today magazine. It is
also observed throughout much of Canada.
The US has about 63,000 pizzerias and 94% of Americans eat pizza at
least once a month. About three billion pizzas are sold in the
United States every year, plus an additional one billion frozen
pizzas. That works out to about 100 acres of pizza per day, or 350
slices per second.