 Gradually , beginning in the 19th century , sheep production in the U.S. moved westward . Today , the vast majority of flocks reside on Western range lands . During this westward migration of the industry , competition between sheep ( sometime called " range maggots " ) and cattle operations grew more heated , eventually erupting into range wars . Other than simple competition for grazing and water rights , cattlemen believed that the secretions of the foot glands of sheep made cattle unwilling to graze on places where sheep had stepped . As sheep production centered on the U.S. western ranges , it became associated with other parts of Western culture , such as the rodeo . In modern America , a minor event in rodeos is mutton busting , in which children compete to see who can stay atop a sheep the longest before falling off . Another effect of the westward movement of sheep flocks in North America was the decline of wild species such as Bighorn sheep ( O. canadesis ) . Most diseases of domestic sheep are transmittable to wild ovines , and such diseases , along with overgrazing and habitat loss , are named as primary factors in the plummeting numbers of wild sheep . Sheep production peaked in North America during the 1940s and 1950s at more than 55 million head . By 2013 the number of sheep in the United States was 10 percent what it had been in the early 1940s . 
