When white settlers started to arrive in large numbers in the mid-1800's, there were substantial populations of bighorn sheep in nearly all the mountainous regions of present-day Arizona except the Navajo country and southeast corner of the state. Bighorn sheep numbers dropped sharply as the human population rose. This was due to many factors:  1) Devastating diseases were introduced by domestic livestock  2) Excessive market and subsistence hunting by miners, railroad workers, and other settlers  3) Fouling or denying of traditional water sources by nearby human activity. Shortly after the turn of the century, the bighorn's range had been reduced to the arid southwest portion of the state and the Grand Canyon, with the exception of small, isolated herds in a half dozen remote locations Bighorn sheep were protected in the Arizona Territory as early as 1887. This protected status did not lead to an increase in numbers, however, and in 1937 the statewide population outside the Grand Canyon and Lake Mead areas was estimated at no more than 700 animals. The establishment of the Kofa and Cabeza Prieta National Wildlife Refuges in 1939 set aside 1.5 milliion acres of the southwest Arizona for the desert bighorn sheep and other wildlife. Further help came with the formation of the Organ Pipe National Monument, Lake Mead National Recreation Area, and the Havasu and Imperial  National Wildlife Refuges. The statewide population of bighorn sheep had grown to an estimated 1080 animals by 1950, the year that Arizona Game and Fish Department wildlife biologist John Russo began his five-year study that formed the basis for modern bighorn sheep management in Arizona. Bighorn numbers in the state increased very little, if at all, over the next several years.  The Arizona Desert Bighorn Sheep Society (ADBSS) was formed by a group of sportsmen in a effort to help wildlife and land use agencies implement Russo's findings and achieve a significant increase in the state's bighorn sheep population.   Back to Facts & Info.