Each year, millions of children eagerly anticipate following Santa Claus’ journey around the globe with the help of the NORAD Santa Tracker. This beloved tradition uses military radar technology to keep tabs on Santa as he delivers presents to well-behaved children everywhere. What many might not realize is that this charming custom began more than half a century ago, thanks to a simple typo in a Colorado newspaper advertisement.

Back in 1955, Sears Roebuck & Co. published an ad in a newspaper in the Colorado Springs area, inviting children to call a number to speak directly with Santa. However, due to a printing error, the number provided connected callers not to the North Pole, but to the desk of Col. Harry Shoup, the director of operations at the Continental Air Defense Command.

Terri Van Keuren, one of Col. Shoup’s daughters, remembers the significance of that particular phone.

“The number was highly confidential, known only to a four-star general at the Pentagon and my father,” Van Keuren shared with StoryCorps during a visit with her siblings to recount the origins of the Santa tracking tradition.

When the phone rang one December day, Col. Shoup was taken aback to hear a child’s voice asking for Santa. Initially caught off guard by the unexpected call, Shoup decided to play along, as his children recounted to StoryCorps. As more calls poured in, he instructed airmen to man the phones, responding as if they were Santa. On Christmas Eve, the airmen even added a depiction of Santa’s sleigh to the command center’s flight monitoring board, which tracked aircraft over the United States.

“Soon after, Dad contacted a radio station and announced, ‘This is the commander at the Combat Alert Center, and we have an unidentified flying object. It appears to be a sleigh.’ Radio stations began calling him hourly, asking, ‘Where’s Santa now?'” Van Keuren explained.

And so a tradition was born.

Shoup’s children say he received letters from all over the world thanking him for having a sense of humor and starting a tradition loved by so many.

The North American Aerospace Defense Command (NORAD) took over responsibility for tracking Santa in 1958. To this day, NORAD staff members, as well as family and friends, volunteer their time to help respond to children’s calls, letter and emails and track Santa’s flight each Christmas.