Mt. McKinley is a big isolated mountain. It rises out of level lowlands to north and south which are but 2,000 and 1,000 feet high respectively, making it one of the world's greatest isolated uplifts out of low country. The steep mass of the peak itself rises 15,000 feet from its base at the head of Ruth Glacier on the south and almost exactly the same from Peters Glacier on the north. McKinley's two most effective bulwarks against the climber over the years have been its distance from the road on the north (29 miles) and the railroad on the south (45 miles) --(both airline distances, far, far less than the winding walking routes require)---and the regulations of the government which for many years prohibited ski-plane landings or airdrop of supplies anywhere on the peak or its approaches, except by scientific espeditions.