History Of Diamond Bell Ranch

Diamond Bell Ranch

Fee lands: 191 acres

State grazing lease: 29,904 acres

BLM federal grazing permit: 798 acres Cost: $897,730

Acquired: March 14, 2008

Fund: 2004 Bond Funds


Today’s Diamond Bell Ranch was once part of the vast Robles Ranch, which was established in 1882 by Bernabe Robles (b.1857 in Baviacora, Sonora, Mexico, d.ca 1945 in Tucson). Robles Ranch was once one of Arizona’s largest cattle ranching operations: the 1.5 million acre “El Rancho Viejo” stretched from Florence to the Superstition Mountains to the Mexican border from 1889 to 1918. Following severe drought and overstocking of livestock in late 1800s and early 20th century, the ranch began to be sold off. By 1949, Robles Ranch was reduced to only 50 square miles, and by the mid-1980s, the ranch was sold and broken into small parcels.

From the 1950s to the 1970s, the area of the current Diamond Bell Ranch was known as the O-Bar-J Ranch. In 1979, the Chilton family bought the ranch, and purchased an additional 4,000 acres to the north around 1990. The northern part of the ranch called Diamond Bell Ranch, was sold after failed efforts in the late 1960s and 1970s to develop the entire ranch into a high- density subdivision. Diamond Bell Ranch became part of the Chilton Ranch and Cattle Company and managed by the Chilton family as a cattle ranch from 1979 to the present.

Biological Resources

The majority of the property is located at lower elevations northwest of the Sierrita Mountains and drainages on the property run west from this mountain range towards the Altar Wash. Most of the property supports semi-desert grasslands with the exception of Valencia Mountain, which supports a diversity of plant communities. The property is entirely within the Conservation Lands System categories of Biological Core, Multiple Use, and Special Species Management Area for the

Rancher Tom Chilton holding a monitoring sign on Diamond Bell Ranch, with the Babaquivari Mountains and Kitt Peak Observatory in the background. Photo by John Sullivan.


The Diamond Bell Ranch differs from other ranches the County has purchased in that 97 percent of the ranch is on State Trust land, which is managed by the County under a State grazing lease, two percent is on federal BLM land, also managed by the County under a federal grazing permit, and less than one percent is actually owned by the County. That said, this property was important to conserve because the County and others have had a difficult time protecting land that contains Pima pineapple cactus, a federally listed endangered species, and Diamond Bell Ranch contains a healthy population of the cactus. Although there are no assurances that the State Land Department won’t sell the State Trust land in the future, the current approach enables the County to manage the land for conservation so long as the grazing leases continue to be renewed. Diamond Bell Ranch is also important for conservation because it is one link
in a system of County and federal conservation areas all the
way from Ajo Highway to the Mexican border along Highway 286. Another unique aspect about the ranch is that it surrounds a residential subdivision of which more than 6,000 acres worth of lots are undeveloped and remain vacant after more than twenty years after initial subdivision.

The property contains a healthy population of endangered Pima pineapple cactus, and habitat to support other Priority Vulnerable Species including Swainson’s Hawk, California leaf-nosed bat, desert box turtle and Ground snake.


The ranch is being maintained as a working landscape. The State grazing leases are being conservatively grazed under a Ranch Management Agreement with rancher Tom Chilton. Permanent monitoring plots have been expanded on the ranch to better measure forage production and track plant diversity and abundance across the ecological units of the ranch. New fences

and enhanced water system elements are being added. The State grazing leases are open for use under the rules and regulations established by the State.


Recreation in the area is primarily the outdoor activities of hiking, mountain biking, hunting, wildlife watching, off highway vehicle travel and some recreational mining. Roads in the area are limited and not maintained for public uses. Access can be limited due to weather conditions and can require 4-wheel drive vehicles. Visitors should be well versed in outdoor travel and not expect to find travel signage or readily available assistance.

Rocky habitat on the western slopes of Valencia Mountain within the Sierrita Mountain range, looking across the southern portion of Diamond Bell Ranch. Photo by EPG, Inc.

Ongoing Property Improvements

• Fence repairs and construction to enhance livestock pasture uses.

• Water systems have been enhanced to provide year-round wildlife waters.

• Vandalism is an ongoing issue so routine monitoring by the operator and county staff identify wildcat trash sites, cut fences, unauthorized off road vehicle travel points and trash left by illegal border crossers and humanitarian aid groups.

Cluster of Pima pineapple cacti in bloom, Diamond Bell Ranch. Photo by EPG, Inc.

Male desert tortoise on the western slopes of Valencia Mountain within the Sierrita Mountain range. Photo by EPG, Inc.