RANGE CREEK CANYON, Utah -- To get to work each day, Mark Connolly drives for more than an hour over winding, treacherous roads into the depths of this juniper-filled canyon. Then he straps on a .40-caliber Glock, adjusts his satellite phone, and heads out on patrol.

Mr. Connolly's beat: 45,000 acres of some of the most rugged and inaccessible terrain in the West, where he watches over a trove of Indian artifacts that date back a thousand years.

"Mark's on his own out there," says Alan Green, a lieutenant with the Utah Division of Wildlife Resources, which employs Mr. Connolly. "Help is often a long way away. This is a really big job."

Mr. Connolly is an archaeology cop, one of a handful in the U.S. who act as the only line of defense against an archaeological site being plundered by looters and losing its historical value. The federal National Park Service has several such cops on staff to protect places like the Anasazi cliff ruins in Colorado's Mesa Verde National Park. The Bureau of Indian Affairs also has archaeology officers to guard Native American ruins in reservations in the Southwest. In Utah, the U.S. Bureau of Land Management has about 15 officers assigned to patrol federal lands and to protect archaeological sites.

Mr. Connolly is the lone archaeology cop employed by the state of Utah. The site he watches over, Range Creek Canyon, is about 150 miles southeast of Salt Lake City. Fremont Indians inhabited the area between 500 A.D. and 1350 A.D. before disappearing from the canyon, possibly after a prolonged drought or because other tribes drove them out, experts say. The Indians left behind artifacts such as pottery shards, food granaries, remnants of stone homes called pithouses, and numerous rock drawings known as petroglyphs and pictographs. In 1951, rancher Waldo Wilcox, his father and brother bought the canyon lands from another rancher, and the artifacts remained hidden for the next half century. Today, these ruins in eastern Utah are mostly undisturbed.

When Mr. Wilcox deeded the canyon to the public in 2002 for $2.5 million as part of a conservation deal, government officials scrambled to safeguard its treasures. Preservation is important for the state: An estimated 80% of the 50,000 known archaeological sites in Utah have been looted over the past century, says Garth Portillo, a BLM archaeologist in Salt Lake City. The state's solution: hire a cop to patrol the canyon. (While officials allow some items to be removed and placed in local museums, they want to preserve the site as is.)

The search led the state to Mr. Connolly. The 53-year-old resident of the nearby town of Price had worked for 24 years as a Utah game warden, during which time he says he had been shot at, confronted by bears and subjected to other risks. After being retired for the last six years, he was itching to do something new. "Here was an opportunity for me to protect the things I care so much about," says Mr. Connolly, who lost 15 pounds within a month of starting the job last April.

The job, which pays $33,000 to $49,000 a year, comes with plenty of hazards. For one thing, there's the matter of driving into the canyon over an 8,200-foot-high pass with drop-offs of hundreds of feet. There's also the danger of being the lone cop in an area where bands of outlaws have been known to roam. "It's the Wild West out there," says Jenny Parks, a director for the Trust for Public Land, a nonprofit conservation group in San Francisco.

Keeping the canyon's artifacts out of the hands of looters requires detective work amid few clues. Former BLM investigator Rudy Mauldin, for example, says he and other federal agents once used DNA from a cigarette butt left at one looting site in Utah to help link the theft of artifacts to a local man, Earl Shumway. In 1995, Mr. Shumway was convicted and sentenced to five years in prison on federal charges of looting several archaeological sites.

Mr. Connolly's approach against plunderers relies more on muscle and the appearance of firepower. On patrols in an all-terrain-vehicle, the Illinois transplant arms himself with a shotgun and a M14 assault rifle in addition to his pistol.

He enters the canyon daily to discourage would-be thieves, a technique that is considered unusual. Other archaeology cops patrol wider swaths of land and so can't be as omnipresent as Mr. Connolly. Observers say Mr. Connolly's constant presence is effective. "If someone is watching you, that is a huge deterrent," says Corinne Springer, who oversees the Wilcox family's former ranch buildings at one end of the 20-mile-long canyon.

Mr. Connolly says his methods pay off. A few months ago, he recalled that he overheard two men at a nearby campground excitedly discussing an ancient stone bowl they had seen in the canyon. Such a bowl can be worth hundreds of dollars. Mr. Connolly, dressed in his uniform, says he walked up to them to ask, "'Hey, did you guys see that stone bowl?' and you could tell by the looks on their faces they had been thinking about taking it." He says the men were scared and left empty-handed soon after.

Mr. Connolly sometimes takes visitors into his confidence in hopes they will share his passion for preserving the canyon. He recently hiked up to some rocks where four men and two women from California were looking for Fremont ruins. After chatting with the group, he decided he could trust them.

"Do you want a thrill?" he asked them. After a strenuous 15-minute hike, Mr. Connolly and the group emerged atop a mesa that contains the stone foundation of a pithouse with remnants of native tools strewn around. "This is like finding Atlantis," said one of the hikers, Jefferson Edmonds, a San Diego psychologist.

Mr. Connolly made the hikers promise not to divulge the location of the pithouse. As dusk neared, he drove out of the canyon, pausing atop one pass. "I always stop here to thank the canyon for the experience," he says.