Decades ago, Mimi Webb Miller ran horseback tours here, entertaining travelers with excursions across the boundary separating Presidio, Tex., from Ojinaga, Mexico, to one of Mexico’s most beautiful and least visited regions.

That was before the death of a romantic partner, one of Mexico’s most notorious drug lords, and fears that she herself might be in danger prompted her to leave the region.

Now she’s back, leading tours again, taking visitors to see what are essentially the most dramatic landmarks of her life. And she feels at home.

“I feel more myself when I’m in Mexico,” she told a group of six tourists, aged 6 to the mid-60s, over breakfast on a recent trip in Ojinaga.

It was our first stop on a weekend tour of the rugged canyons and tiny towns of northern Mexico, including San Carlos, a popular vacation destination known for its waterfalls. And it marked Webb Miller’s first trip across the border in several years.

Webb Miller, 65, grew up in Wichita Falls, a debutante from a prominent Texas family; her uncle was a former United States senator, John G. Tower. She divides time between Terlingua, where she owns a guesthouse, and Venice, Calif., where she works as a casting director for commercials.

But Webb Miller spent most of her 20s and 30s in the remotest corners of West Texas and northern Mexico, hanging out with customs agents and drug smugglers. For some tourists, Webb Miller’s frank stories about the area’s troubled history are as alluring as the area’s natural beauty.

Webb Miller first came to the Big Bend region in the 1970s. Entranced, she bought a ranch in Mexico and fell in love with a Mexican man who became her common-law husband. She raised goats, bathed in waterfalls, and took American tourists on horseback trips through Mexico’s many canyons. Sometimes, the nearest telephone was a two-hour drive away on washed-out roads.

But the border region that Webb Miller loved was also deeply affected by the illegal drug trade, and many sought her as a tour guide, in part because of her firsthand understanding of its impact on the area.

In the 1980s, one of Webb Miller’s neighbors was Pablo Acosta, the kingpin who then controlled drug traffic along 200 miles of the border. Though Acosta had been linked to several murders, Webb Miller said she found him kind and conscientious. Fiercely proud of the small northern Mexico towns like the one where he grew up, Acosta helped Webb Miller obtain permission to cross the border for her horseback trips, and the two became friends.

After Webb Miller’s relationship with her common-law husband fell apart, she briefly dated a customs agent stationed in Big Bend National Park— “the narc in the park,” she called him — then took up with Acosta.

“He was kind of like Kissinger,” Webb Miller said of Acosta. “Not the handsomest man I’d ever met, but a strong guy, with a lot of charisma.”

Romantic involvement with both a customs agent and a drug lord might have seemed incongruous, but somehow it made sense to her: Both were products of the region she loved.

She was dating Acosta when he was killed in a helicopter shootout with Mexican federal police in 1987. After his death, Webb Miller said, Sheriff Rick Thompson of Presidio County told her there was a price on her head, because she knew so much about the region’s drug trade.

(Four years later, Thompson was charged with smuggling more than a ton of cocaine across the border; he is serving a life sentence.)

Heartbroken and afraid, Webb Miller fled to California.

But cartel violence in northern Mexico has begun to wane. Ciudad Juárez, which had the highest murder rate in the world from 2008-10, had dropped to No. 37 by 2013. So Webb Miller decided it was time to bring tourists back to visit the waterfalls and friendly towns of the rural region. These days, she arranges tours out of Terlingua (population: 60). Excursions range from $150 for a day trip to $500 for a weekend.

Jozef Matheny, a Galveston hairdresser who has taken several of the trips, said border officials recognized Webb Miller by name. “At the border they looked at her passport and said, ‘Are you that Mimi?’ ”

After gathering supplies, the group headed east toward San Carlos in its three four-wheel drive vehicles. The two-lane road traced the shape of the Rio Grande as the Chisos Mountains loomed in the distance.

While the group set up camp by a creek near a stand of huge cottonwood trees, Noemi Aviles, Webb Miller’s assistant, harvested figs to share.

Beyond San Carlos, the paved road gave way to rutted gravel. At one point, the caravan stopped to let a mare and her colt gallop across. That evening, a few miles outside the small outpost of San Miguel, Aviles lugged out a disco, a large vessel resembling a wok, to make picadillo.

As nighthawks swooped overhead, Webb Miller’s audience leaned in, eager to hear more stories. At times, the proximity to old times has left her close to tears. Someone asked what had brought her and Acosta together. Webb Miller paused, looking into the campfire. “I think Pablo loved me because I loved Mexico,” she said.