Scientists believe that the ancestors of today's horses evolved in North America 3.5 million years ago. Those animals became extinct in the Americas at least 11,000 years ago, and it wasn’t until the early sixteenth century that Spanish explorers and missionaries reintroduced horses into the American West. By 1700, Northwest tribes had horses. Within a hundred years, wild horses again populated the plains, while modern breeds eventually diluted or replaced most of the Spanish strains.

The number of wild horses and burros diminished significantly during the decades of western settlement, as people encroached on their range and exploited the animals for commercial purposes. During the 1950s and 1960s, Velma B. Johnston, known as “Wild Horse Annie,” ran a grassroots campaign in Nevada that led to the Wild Free-Roaming Horses and Burros Act of 1971. The act requires the protection, management, and study of "unbranded and unclaimed horses and burros on public lands in the United States," and the Bureau of Land Management was given the responsibility for managing the Wild Horse & Burro Program (WH&B).

In southeastern Oregon, the BLM now manages 18 Herd Management Areas (HMAs) and co-manages one Wild Horse Territory with the U.S. Forest Service. In 2023, an estimated 4,519 wild horses and 54 wild burros were roaming on Oregon’s HMAs and the Wild Horse Territory, 75 percent more than the BLM’s recommended population of 2,690 animals.

Normally, three to five of Oregon’s HMAs are gathered annually to remove excess animals and balance population numbers with the range’s capacity to sustain them. Animals removed from the Oregon range are taken to the Wild Horse Corral Facility near Burns, where over 16,000 animals have been prepared for the adoption program. The adoption program, however, has never kept pace with the number of animals available. Annual adoptions fell from a high of 8,000 per year in the early 2000s to about 3,500 in 2017.

Those animals that are not suitable for adoption are sent to federally funded sanctuaries or long-term holding facilities, where they live out their lives on the prairie. The Burns facility held fewer than 550 long-term horses in 2017, so many Oregon horses were sent to pastures in the Midwest. In January 2018, 50,935 horses and burros were in off-range pastures and corrals, requiring $48.6 million (58 percent of the program budget) to support them.

Known for their quality and color, Oregon's wild horses are popular with those who adopt wild horses. Some of the most admired horses are the Kiger Mustangs on Steens Mountain. DNA testing has demonstrated that Kiger mustangs are largely descended from the Spanish horses brought to North America in the seventeenth century; and their beauty, athletic ability, and historic importance make them a significant part of the western heritage. Periodically, horses from the Kiger herd are exchanged with the Riddle Mountain herd to preserve their bloodline while maintaining genetic diversity. To maintain the core of the breeding herd, quality animals with dun factor coloration and Spanish mustang characteristics are returned to the HMAs following the roundups.

Controversy surrounding the WH&B Program was intense from the beginning, but it has increased in recent years due to the expanding population of wild horses. As of March 2018, the BLM estimated that public rangelands were home to nearly 82,000 wild horses and burros, more than three times the recommended maximum of 26,690 animals. In 2017 alone, the population grew by more than 9,000 animals. With no natural predators, wild horse and burro populations could double in size by 2023, a situation that would almost certainly lead to an ecological disaster as animals die of starvation and a lack of water.

The BLM is caught in gridlock of lawsuits filed that have hindered the agency’s ability to take action. Advocacy groups question BLM’s management goals and methods. They argue that many herds are already too small to support genetic diversity and long-term health, that roundups are inhumane and impoundment is unethical, and that commercial sheep and cattle grazing should be reduced or eliminated to make more forage available. Ranchers counter that livestock grazing on public lands is a historic, legitimate use of public land and is mandated by law, and livestock removal would only be helpful until the horse population grew to replace current livestock numbers. Wildlife conservation organizations assert that native wildlife species should take precedence over the descendants of domesticated horses, and ecologists point to damage from overgrazing that may lead to the permanent loss of prairie and desert ecosystems.

Wild horse advocates have asked the government to use a fertility control vaccine to suppress reproduction, but the vaccine only lasts one to two years, making it necessary to round up tens of thousands of horses each year to administer the vaccine. The BLM office in Burns began testing a sterilization procedure on mares from the Warm Springs herd in 2016 and again in 2018, but they abandoned both efforts after a coalition of advocacy groups challenged them in court.

Due to spiraling costs, some horses have been sold under a 2005 act that directs the BLM to sell “without limitation” animals that are over ten years old or have been offered three times for adoption. Nearly 1,800 wild horses were sold to a buyer, who then sold them to slaughterhouses in Mexico, causing an outcry and tighter control of direct sales.

Wild horses and burros represent the diverse history and pioneer spirit of Oregon and the West. Despite the controversy and strategic challenges, Oregonians can still see them running through some of the last open spaces of the frontier.