Colorado's central and southern mountains still draw droves of skiers to the slopes. However, many of the historic runs and areas that were popular over the past century, some near the current resorts of Aspen, Breckenridge, Crested Butte, Purgatory, Telluride, and Vail, no longer exist. Local hills like Whittaker Ranch near Eagle featured little more than a rope tow and warming hut. Now underneath Lake Dillon, Prestrud Jump hosted tournaments where...