The Ninety-Pound Rucksack Challenge is an annual ski mountaineering event that honors the legacy of the 10th Mountain Division, their historic World War II ascent of Riva Ridge, and their post-war contributions to American skiing. The event entails ascending a ski slope or backcountry route on February 18th at 7:00 p.m. local time—the anniversary of the Riva Ridge ascent.