It's the first Friday in June, and that means it's National Doughnut Day. It's one of those days that everyone loves to celebrate—especially if the local doughnut shop is handing out free doughnuts, but few people know the story behind the holiday.

National Doughnut Day is a recognition of the women from the Salvation Army who were sent to the front lines of the war, World War I, in Europe. These women, who volunteered for the duty, made hot meals for the troops, including freshly made doughnuts. In 1917 Lt. Colonel Helen Purviance as Ensign Purviance, was sent to France. Considered the first "doughnut girl," she and other Salvation Army officers, made homemade doughnuts, rolling out the dough with a wine bottle, and then frying the doughnuts over an open fire. That first day, they made a mere 150 doughnuts, but once they fine tuned the process and created an assembly line, they were frying up to 9,000 hot, fresh doughnuts for servicemen a day.

According to tradition, the doughnuts were often cooked in hot oil heated inside the steel helmets of American infantrymen. These Salvation army "lassies" were the only non-military women allowed to visit the front lines, and they were enormously important in terms of troop morale. Often the Salvation Army set up mobile tents and huts, moving with the army, and distributing food, especially homemade pies and doughnuts, and hot beverages (as well as emergency first aid, and warm clothing made by women back home).

Both DunkinDoughnuts and Krispy Kreme celebrate National Doughnut Day by giving away free doughnuts (you need to buy a beverage at Dunkin Doughnuts). At many doughnut shops, today's proceeds to to the Salvation Army and other charitable causes.