Most Americans view National Doughnut Day – or National Donut Day, depending on who you ask – as an opportunity to snag free snacks at local food chains. Luckily for them, there will be no shortage of free donut offers on Friday. But the event’s origins are actually rooted in charity.

National Donut Day was first celebrated in 1938 as a tribute to a World War I tradition. War rations were notoriously unsatisfying, so members of the Salvation Army, a charitable organization, would bring soldiers free donuts in an attempt to boost their spirits. Held every year on the first Friday in June, this year’s event will be the 78th annual celebration. The Salvation Army spearheaded the event’s creation to raise money for its services during the Great Depression.

“Donuts have a special place in our country’s history and culture, creating moments of delight, lifting spirits and bringing people together at work and at home,” Dunkin’ Brands’ Vice President of Product Innovation Jeff Miller said in a press release. Dunkin’ Donuts will offer a free donut to customers with the purchase of any beverage, one of several such promotions held at national and local donut chains around the country.

To this day, the Salvation Army’s Chicago branch considers National Donut Day a flagship fundraising event. Proceeds from “Donut Day” are used to stock food pantries and other charitable enterprises throughout the greater Chicago area, according to the organization’s website.

Some credit “National Donut Day” with introducing the delectable dessert to mainstream America., a website dedicated to the event, attributes the connection to food historian John T. Edge. “The doughnut traces its roots to Europe, but gained a foothold here when soldiers returned home longing for the treat they were served by Salvation Army Doughnut Girls, a symbol of motherhood and home,” a video on the website said, citing Edge.