In 1971, wild horses and burros were found roaming across 53.8 million acres of Herd Areas (HAs), of which 42.4 million acres were under the BLM's jurisdiction. Today the BLM manages wild horses and burros in subsets of these HAs, known as Herd Management Areas (HMAs) that comprise 31.6 million acres, of which 26.9 million acres are under BLM management.
The Sand Wash HMA is generally located 45 miles west of Craig, Colorado, in the Sand Wash Basin. The boundary of the HMA is fenced, except along State Highway 318, generally preventing wild horses from entering or leaving the HMA. There are no fences within the HMA, allowing horses to roam freely within the confines of the basin.
The Sand Wash HMA includes 154, 940 acres of public land, 1,960 acres of private land, and 840 acres of State school section lands, for a total of 157,730 acres. Sand Wash Basin is surrounded by ridges and mesas. Lookout Mountain on the northeast boundary is the highest point in the HMA at 8,120 feet, and the lowest point is where Sand Wash exits the HMA at an elevation of 5,800 feet. The Sand Wash Basin receives 7 to 12 inches of annual precipitation, and the climate is typical of the cold deserts of the Rocky Mountain Region, with warm summers and very cold winters. Vegetation types within the HMA include sagebrush/bunchgrass, saltbush, and pinyon-juniper woodlands.
The horses within the HMA exhibit many different colors. Among the most common are grey and sorrel, although most colors and color patterns can be found, including buckskins, duns and paint. Genetic analysis indicates the highest similarity for the herd was to the Iberian derived Spanish breeds, followed by Gaited breeds, North American breeds and Arabian breeds.
The original population of horses with the HMA in 1971 was 65 head. The managed population range recommended in 1986 was changed to a maximum of 217 horses in 1995, and again in 2001 to a management range of 163 to 363 horses. The existing horse population has been managed to the most current of these numbers through horse gathers in 1989, 1995, 1998, 2001 and 2005. The herd had a population high of 455 head in 1998. The most recent aerial census conducted in July of 2008 showed a population of 411 head within the HMA.