The first Friday in June has become one of the country's sweetest traditions — it's National Donut Day! For many Americans, the day is little more than a welcome excuse to indulge in fried dough and sugar.

The donut hole has always been more than a neat little circle of missing dough — it's a mystery with multiple claimants to its invention. Dutch settlers brought olykoek, or oily cakes, to early America, but they were heavy, round pastries without holes.