In a private 1972 report to the Director of the National Park Service, Jack Anderson, Superintendent of Yellowstone National Park, confessed that “we are apprehensive that their proposal would ultimately end up with the complete slaughter of all bison, as occurred on the Crow Indian Reservation.”Footnote ¹ For decades, livestock producers at the local and national level pressured park officials to eliminate a specific disease—brucellosis caused by Brucella abortus—from Yellowstone’s buffalo herds. Following World War II, governments targeted this bacterial contagion in American domestic and wild animal populations to improve public health and livestock producers’ profits. Symptoms of brucellosis, which humans can catch from other mammalian hosts, vary across species. For domestic cattle, it can cause spontaneous abortions and, in rare cases, death. Buffalo seem largely unaffected by brucellosis but for humans, the bacterial infection can cause a plethora of chronic and debilitating symptoms.Footnote ²

The incident Jack Anderson was referring to happened several years earlier when federal and state officials destroyed the Apsáalooke (Crow) Tribe’s entire buffalo herd supposedly due to brucellosis concerns.Footnote ³ Due to strict regulations that punish entire counties and states for only a few positive cattle, stock producers and the state of Montana have decried for decades the Yellowstone herds’ positive brucellosis status. Consequently, states and park officials authorize hunts, herding, or capture of bison who stray out of the park to try to prevent the spread of the bacteria to domestic cattle. Elimination of disease from Yellowstone bison herds, however, remains elusive to this day. To the present, no one has conclusively proven that buffalo can spread brucellosis to cattle, but elk can and do, even as they are omitted from regulations.Footnote ⁴

Bison and brucellosis were and continue to be agents of historical change. The planet’s recent experience with the COVID-19 pandemic is a visceral reminder of humanity’s “embeddedness in the animal world.”^{Footnote 5} Within the field of animal history, there exists a growing subfield of research on other-than-humans and their infections.Footnote ⁶ Historians in this field show that diseases—bacterial, viral, protozoan, parasitic, and prionic—affected non-human beings and Homo sapiens in U.S. history. This influence included nation-state borders and transnational relationships, human understandings of space, and settler colonial erasure of the Indigenous.Footnote ⁷ Borders were a tool in addressing animal infections and a point of conflict as microbes and their animal hosts ignored human boundaries like state and national borders, including by disturbing settler attempts to chip away at Indigenous sovereignty.Footnote ⁸ Microbes and animals, to illustrate, obstructed Canadian and American state building by traveling over the border between the two settler countries, despite transnational communication between the nations. Non-humans also brought the national to the local, reducing space, as was the case in the 1914 foot-and-mouth outbreak in Montana. Livestock officials at the local, state, and federal levels, however, relied on strict space and regulation enforcement to control diseases. This included interfering with Indigenous sovereignty, as was the case with the Apsáalooke buffalo herd mentioned by Superintendent Anderson. These three case studies of quarantines and disease regulations of both domestic animals and bison from Montana and Yellowstone provide concrete examples of other-than-human’s roles in unsettling human nation-state boundaries, space, and settler colonialism.

Animals and microbes troubled the attempts of nation-states to impose strict spatial divisions, usually in the form of quarantines, including at the United States-Canadian border.Footnote ⁹ In response to growing knowledge about animals’ infections and their ability to interfere with livestock profits, the United States and Canada lifted and imposed restrictions on the importation of stock animals to control a variety of diseases including scab, glanders, dourine, bovine tuberculosis, and foot-and-mouth (FMD).Footnote ¹⁰ Brucellosis was not of great concern until later in the twentieth century, largely because scientists did not prove it could infect humans until 1918.Footnote ¹¹ In early twentieth-century Montana and the Canadian province of Alberta, disease ran rampant in the livestock herds on the plains where the border remained an imaginary line. Federal and state officials were, on paper, in a cooperative model of regulation enforcement where both governments set and enforced rules governing transport, testing, slaughter and vaccination. States were, however, largely responsible for much of the local level work, especially in rural areas like the plains of Montana. Livestock officials and veterinarians worked throughout the twentieth century to create and enforce rigid delineations between Canadian and American space as a disease control method by literally, in some cases, chasing down animals for inspection.

This border enforcement required intergovernmental communication across the settler boundary. American and Canadian officials, especially Montana and Alberta government veterinarians and agents, communicated extensively to prevent diseased animals from crossing the border. At times, the correspondence between the settler veterinarians was collegial and educational, where officials exchanged ideas and regulatory information about the disease control methods of their respective governments.Footnote ¹² Yet, as Montana veterinary officials noted, there was also tension and animosity among these officials, often caused and exacerbated by hundreds of miles of open borders on the North American prairie. One Montana livestock official in 1911 described the border as, “unsettled.”Footnote ¹³ The imprecise boundaries led to several quarrels between the groups of officials, as was the case in 1911 when each tried to foist responsibility to the other government for capturing and killing diseased horses at the border.Footnote ¹⁴ Trying to manage stock movement across the 49^th parallel to control diseases facilitated communication between nation-states, thus revealing the contingent, as well as animal and microbial, nature of nation-building.

These other-than-human actors also contributed to the reworking between the national and the local scale in the nineteenth and twentieth centuries. For example, the cattle industry battled a Foot-And-Mouth (FMD) outbreak across the United States in 1914, and local humans and animals felt its consequences.Footnote ¹⁵ In Montana, cattle caught FMD from other bovines imported from Chicago by rail. The national became local. In the eastern Montana town of Glendive in 1914, residents dug a trench “of death” in the frozen ground.Footnote ¹⁶ State and federal veterinarians and employees then herded hundreds of infected or exposed cattle into the ditch and shot them. Residents isolated their pets away from the pens and burial sites, while officials quarantined all other livestock and then tested and euthanized infected animals. FMD’s spread from Chicago to Montana—helped by the railroad—condensed geographic space from the broad national to the local level. Following the 1914 FMD outbreak, Montana’s livestock officials and veterinarians enjoyed an infusion of funding from the state legislation and more regulations to address animal disease outbreaks.Footnote ¹⁷ Those regulations only gained importance to governments and livestock producers throughout the twentieth century.

The development of animal disease control rules changed human ideas of space as proverbially clean or infected. For example, post-World War II brucellosis regulations named entire regions and states as disease-free or infected based on testing results at the county level, forcing cattle producers living in diseased spaces into mandatory test-and-slaughter and vaccination programs regardless of their individual herd’s test results.Footnote ¹⁸ State governments—in cooperation with federal agencies—were largely responsible for the oversight of these national testing and vaccination brucellosis rules.Footnote ¹⁹ Because of those spatial regulations, Montana veterinary officials, and trade groups like the American Veterinary Medical Association, decried the Yellowstone buffalo herd’s brucellosis-positive status and called for the total eradication of the herd.Footnote ²⁰ As long as the buffalo remained within the park’s borders, surrounding states like Montana, could not shoot or hunt the mammals. Once they crossed the line and potentially threatened a state’s brucellosis regulatory status, however, authority shifted to the state. The National Park Service (NPS), in response, continued to maintain throughout the 1970s that border control methods of shooting or herding buffalo who periodically strayed out of Yellowstone, was the best control for brucellosis, despite local and national livestock groups pressure to destroy all bison. One Park biologist called the solution to the brucellosis problem as “essentially one of boundary control.”Footnote ²¹ NPS officials relied on and affirmed the human-made Yellowstone boundaries to control for brucellosis. In so doing, they also contributed to the delineation of Yellowstone vs. Montana space.

The Brucella infection and the animals that carried it confronted that unseen boundary when bison habitually left the Park, despite shootings or hazing. Park and state officials have tried various hazing techniques like loud noises or herding with horses for decades with limited effectiveness. One report described how once buffalo became used to the control measures, “they no longer responded.”Footnote ²² As the element of surprise wore off, the massive mammals went back to ignoring the human-imposed boundaries in their search of winter grass. Discounting human control measures centered around enclosing and enforcing artificial spatial boundaries, bison unsettled human attempts at enforcing strict spatial divisions and stricter brucellosis regulations.

Federal and state government officials turned those regulations against the Apsáalooke tribe’s bison herd in the 1950s and 1960s, challenging Tribal sovereignty on the Crow Reservation, east of Yellowstone.Footnote ²³ Local stockmen and government officials called for the destruction of the herd. The Crow buffalo did carry brucellosis, even though Tribal members questioned whether the disease hurt the animals.Footnote ²⁴ Instead, Joe Medicine Crow—a respected Apsáalooke leader, historian, and war hero—claimed that the real agenda of bison destruction had little to do with bacteria. Instead, “the cattlemen,” Medicine Crow believed, “wanted to get the land.”Footnote ²⁵ Despite Indigenous opposition, beginning in 1962, federal and state employees destroyed the herd, until “a poacher” in 1965 shot the last bison.Footnote ²⁶ In opposition to stockmen wanting to graze on or buy the former buffalo pasture, the tribe reestablished their herd seven years later, this time with brucellosis-free buffalo from Theodore Roosevelt National Park.Footnote ²⁷ The Apsáalooke Tribe’s loss of its buffalo herd in the 1960s shows how settlers challenged and tried to erase sovereign Tribal space for disease control.

Over two hundred miles from the Apsáalooke herd, border enforcement as disease control for the Yellowstone bison, who remained brucellosis-positive, continued throughout the rest of the twentieth century. Boundary control through hazing, hunting, and capture persisted as the primary way NPS officials prevent bison contact with domestic cattle. Buffalo and brucellosis continued to ignore those borders, often straying out of the park during hard winters in search of grass. Their actions caused increasingly bitter fights between producers, Montana state representatives, pro-buffalo protestors, Indigenous peoples, and park officials. To object to bison slaughter and hunting, a protestor in 1997 threw a five-gallon bucket of buffalo entrails onto a table in front of the governor of Montana, two US senators, and the US Secretary of Agriculture.Footnote ²⁸ Since then, because of intensive work on the part of many stakeholders, a new regulatory zone was created around the park for livestock in 2011. Now, stock producers in this area undergo extra testing, but if their stock test positive for brucellosis, the entire state’s brucellosis status is not threatened.Footnote ²⁹ This regulation is another expression of disease livestock officials’ and producers’ use of borders and area controls that began with other diseases in the early twentieth century. Despite these changes, the issue remains controversial, with the tenuous consensus on the verge of collapse, due to increasing enmity from Montana’s Republican governor towards a proposed new management plan.Footnote ³⁰

Animals and microbes have affected historical nation-states and transnational correspondence, human understandings of space, and settler-colonial attempts to interfere with Indigenous sovereign spaces. Animals—bison, cattle, and horses, and their various hitchhiking microbes—ignored and elicited changes in human attempts to establish firm spatial and national settler colonial boundaries. Much generative research remains for historians at the intersection of non-humans and their spaces.

Questions remain relative to nation and government building and transnationalism, about the roles of animals, disease, and officials that tried to contain them. What roles did livestock officials play in the rise of nationalism and the enforcement of boundaries between countries? Initial research and case studies, such as the ones mentioned above, show that as animals and microbes behaved in unruly ways, they challenged divisions between nation-states. Furthermore, in what ways did government agents at various levels understand their role in enforcing these strict borders while also connecting scientific and agricultural communities across borders? How did animals and their diseases reshape space? Research addressing these questions by incorporating the other-than-human stands to complexify and confront historical narratives about the development of nation-states and borders. Finally, there are opportunities for research at the intersection of settler colonial histories and non-humans. How did settlers use animal disease regulations to challenge Indigenous sovereignty in the United States? Conversely, how did Indigenous peoples draw on their relationships with other-than-human relations like horses, to respond to settler colonialism and new zoonotic infections? Examining the intersections of Indigenous and animal disease histories will provide compelling research provides critical expansion of understandings of Indigenous and non-humans in American histories.

The intertwining of diseases between species and consequently, human cultures and governments, further pushes the boundaries of historical thinking about separations between nation-states and transnationalism, production of borders and space, and settler colonialism. Animals and their microbes complicated the division between the local and the national, illustrated by the 1914 FMD outbreak in Montana. Later, bison and brucellosis challenged spatial disease rules by migrating over borders. The mobility of buffalo and bacteria led to both cooperation and conflict between federal, state, Tribal, and local stakeholders. Accounting for the non-human within modern U.S. history upsets historical narratives of human control and power. Examining animals and their microbes as historical agents shows that humans are members—not owners—of layered histories created by complex give-and-takes between species.