The Iditarod is a sled dog race across Alaska. Some key rules are that mushers must pull over and wait if another musher is within 50 yards, dogs must have microchips implanted for identification, and mushers can have up to 16 dogs but must use at least 12 at a time. The race was started to deliver medicine by dog sled after a disease outbreak when other transportation was not possible due to frozen water and thick snow.