The American Birkebeiner cross-country ski race

Since it was first held 50 years ago, the American Birkebeiner, a trek of more than 30 miles through the Northwoods of Wisconsin, modeled after a fabled bit of Norwegian history, has become the largest cross-country ski race in the U.S. Correspondent Conor Knighton reports on how enthusiasm for the festival of events surrounding the race (dubbed "Birke fever") has snowballed.