Doughnut devotees, mark your calendars and save your appetite. This Friday, Chicago is set to join the nation in celebrating National Doughnut Day, and local doughnut chains are geared up to sweeten the deal. Krispy Kreme, Dunkin', and other favorite outlets are offering special promotions to honor the occasion.

Originating in Chicago back in 1938, National Doughnut Day pays tribute to the Salvation Army "Donut Lassies," who boosted soldiers' spirits with these treats during World War I. NBC Chicago reports that these women braved tough conditions to provide a taste of home to troops on the front lines, dishing out thousands of doughnuts in makeshift huts. It's a day entrenched in tradition, evolving from a heartwarming wartime gesture to a modern-day celebration of the beloved sweet.

Leading the pack, Krispy Kreme is offering one free doughnut of any flavor to every customer this Friday, with no purchase necessary. Additionally, Krispy Kreme sweetens the pot by offering a dozen original glazed doughnuts for just $2 when patrons buy any dozen, as per an announcement by the chain. The company emphasizes that the deal is in-store only and available while supplies last.

Not to be outdone, Dunkin' has its own National Doughnut Day treat lined up. According to FOX 26 Houston, Dunkin' fans can snag a free classic doughnut with the purchase of any beverage throughout the day. Meanwhile, 7-Eleven extends the celebration to loyalty members, offering $1 glazed doughnuts at participating 7-Eleven, Speedway, and Stripes stores.

Local favorite Duck Donuts joins in with an offer that is sure to attract a line: a complimentary cinnamon sugar doughnut, no strings attached. And for those craving a glazed treat, Shipley Do-Nuts invites customers to enjoy a free glazed doughnut with any purchase made on the day. These offers are also available only in-store at participating locations.