ST. PAUL, Minn. - Friday's National Donut Day has a long history.

The Chicago Salvation Army first started the annual celebration in 1938, to honor the women who served doughnuts to soldiers on the front lines during World War I. They're credited with helping to lead the donut to its popularity back home in the U-S. National Donut Day is now traditionally celebrated on the first Friday of June.

In the Twin Cities, the Salvation Army is recognizing the history of the day, at the opening of the WWI America exhibit at the Minnesota History Center in St. Paul. The Salvation Army will be giving away free donuts, while supplies last, starting at 7 a.m.

Several other places are also offering free donuts to customers on Friday, in honor of National Donut Day:

- Cub Foods is giving away a free donut to every customer, with no coupon or other purchase required.

- Dunkin' Donuts is also giving customers a free classic donut, with purchase of any beverage, while supplies last.

- Tim Horton's is offering a similar deal, with a free classic donut with any coffee purchase.

- SuperAmerica customers can get a free glazed ring donut by showing this tweet at checkout.

- KwikTrip customers can send a text for a free donut coupon.