Volunteers at the home of the North American Aerospace Defense Command are getting in the Christmas spirit. 

Pulling on their Santa hats with the phone lines in place, the Christmas elves at NORAD are primed for their 57th annual goodwill mission. 

The first shift of Santa trackers start taking calls early Monday at 877-HI-NORAD (877-446-6723), telling children — and some adults — when Santa is due at their house. The last shift won't end until nearly 24 hours later.

They'll also post updates online, on Facebook, and Twitter.

The volunteers will work from Peterson Air Force Base in Colorado Springs, Colo.

NORAD, a joint U.S.-Canada command responsible for protecting the skies over both nations, says its Santa-tracking rite was born of a humble typo in a newspaper ad in 1955.

The ad in a Colorado Springs newspaper invited children to call Santa but inadvertently listed the phone number for the Continental Air Defense Command, NORAD's predecessor, also based in Colorado Springs.

CONAD officers played along, and word spread that this Cold War military command charged with guarding the U.S. against an attack by the Soviet Union was also telling kids where Santa was.

Since then, NORAD Tracks Santa has gone global, progressing through bulletins on AM radios and black-and-white TVs to updates on Facebook, Twitter and smartphone aps.

Last year, volunteers answered almost 102,000 calls, nearly 25 percent more than the previous year. They also answered more than 7,700 emails (noradtrackssanta(at)outlook.com).

The NORAD Tracks Santa website attracted 18.9 million unique visitors from 220 countries and territories during December 2011.

This year, the program had more than 1 million likes on Facebook and nearly 97,000 followers on Twitter days before the tracking operation got under way.

Based on reporting by the Associated Press.

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