Note: This article has been updated to reflect the fact that U.S. Ski Team member Jessie Diggins was the top American in four consecutive U.S. nationals races in 2012, winning the freestyle sprint, 10 k skate and 20 k classic mass start outright and placing second to Canada’s Dasha Gaiazova in the classic sprint (but topping the podium as the first American). This week, Caitlin Patterson, of the Craftsbury Green Racing Project, became the first...