Priority Fund The American Birkebeiner is America's largest cross-country ski marathon, with a course spanning from Cable to Hayward. It attracts over 10,000 skiers and part of the Worldloppet Circuit and American Ski Marathon series. This Fund supports the operations of the American Birkebeiner Ski Foundation and the Foundation for the Endowment of the American Birkebeiner. Since this is an Agency Endowment Fund, donations must be made through the Endowment for the American Birkebeiner website.