A view of the Eldora Mountain Resort base area from the lower part of the Cannonball lift. Credit: Kamen G.A view of the Eldora Mountain Resort base area from the lower part of the Cannonball lift. Credit: Kamen G.Boulder County’s sole ski resort is being put up for sale. One-third of Colorado’s ski resorts are owned by just four companies, according to the National Ski Areas Association. Local investors bought the Vermont ski areas.