Mammoth Mountain opens early and some years doesn't close until the Fourth of July. Mammoth has snowmaking to the top of its highest peak (more than 11,000 feet) and down the Cornice Run. Mammoth is exactly what its name implies: BIG. OK, so how big is it? 3,500 acres to play on, a vertical drop of 3,100 feet, access to lift skiing at 11,053 feet, 156 trails and 27 lifts (9 of which are high-speed zappers). There is an average of 300 days of sunshine a year here.