For many families in New Glarus, Christmas Eve isn’t complete without keeping an eye on the sky. As children here wait for the sound of sleigh bells echoing off the hills above town, there is one place that offers the most reliable glimpse of Santa’s progress: NORAD Tracks Santa.

The North American Aerospace Defense Command has monitored Santa’s flight since 1955, when a Colorado newspaper accidentally published a military phone number in a holiday ad inviting kids to call Santa. Instead of correcting the mistake, the officers on duty played along, tracking Santa’s location using their systems and giving updates to excited children. Today, the tradition has grown into a full-scale operation with volunteers, radar systems, satellite imagery, and an official website that millions visit every December 24.