The European conquest of North America proceeded in fits and starts from the coasts to the interior. During the early colonial period, the Plains and the Plateau peoples were affected by epidemics of foreign diseases and a slow influx of European trade goods. However, sustained direct interaction between these nations and colonizers did not occur until the 18th century.

In 1738 the Mandan villages on the upper Missouri River hosted a party led by the French trader Pierre Gaultier de Varennes et de la Vérendrye; this is often characterized as the event that initiated lasting contact between the peoples of the northern Plains and the colonial powers. Certainly a significant number of traders, such as David Thompson, were living with the Mandans and other Plains peoples by the late 18th century. Accounts of daily life in the region, gleaned from the diaries and letters of these traders, indicate that the interior nations were adept negotiators who enjoyed a relatively prosperous lifestyle; indeed, many visitors commented on the snug nature of the earth lodges in which Plains families lived and on the productivity they witnessed in the region. Although somewhat less historical data exists for the Plateau peoples of this era, it is clear that the 18th century was a time of great change for both groups. Three key factors influenced the trajectory of change: the arrival of horses, the arrival of guns, and the arrival of native peoples from adjacent culture areas.

Horses were introduced to the Americas by the Spanish conquistadors. The advantages of using horses, whether as pack animals or as mounts, were obvious to the Plains and Plateau peoples, who had until then been obligated to travel overland by foot or in small boats on the regions’ few navigable rivers. Horses might be acquired in one of several ways: through purchase or trade, by capture from a rival group, or by taming animals from the wild herds that soon arose.

The dense forests of the Northeast, Southeast, and Subarctic had discouraged the widespread use of horses; in those regions, abundant waterways provided a more readily negotiated system of transportation. Thus, horses spread from the Southwest culture area to the Plains and the Plateau following a northerly and easterly trajectory. As horses spread, the pedestrian foragers of the southwestern Plains quickly incorporated them into bison hunts. Previously these had been dangerous affairs: the range of the bow and arrow was not great and so required hunters to approach animals rather closely, while the alternative method of hunting was to stampede a herd of bison toward a cliff, from which they would fall to their deaths. The speed and mobility provided by horses were great improvements over these earlier conditions.

Spanish law expressly forbade the distribution of firearms to Indigenous individuals, but the English and Dutch traded them freely. Initially used in battle and to hunt the large game of the eastern and boreal forests, firearms were readily incorporated into the bison hunt by the pedestrian forager-farmers of the northeastern Plains. The horse’s speed and agility had inspired a more effective form of hunting in the southern Plains; in the north a similar increase in productivity occurred as guns replaced bows and arrows. A rifle’s greater firepower allowed more distance between hunter and hunted, lessening the danger of attack from a charging animal.

Horses and guns spread to the interior over the course of about 100 years, from roughly 1600 to 1700. By approximately 1700 many tribes were moving to the interior as well. Those from the Northeast were agriculturists pushed west by the intertribal hostilities of the Huron-Algonquian-French and Iroquois-English alliances. Those from the Southwest were Apachean and other hunters and gatherers who, having acquired horses, were able for the first time to match the movement of the bison herds.

By the 1750s the horse culture of the southern interior had met with the gun culture of the northern interior. The combination of guns and horses was invaluable: nations could follow herds of bison across the landscape and also take advantage of the greater distance and power allowed by firearms. From the mid-18th century to the first part of the 19th century, horses and guns enabled the indigenous nations of the North American interior to enjoy an unprecedented level of prosperity.

Removal of the eastern nations

The first full declaration of U.S. policy toward the country’s Indigenous peoples was embodied in the third of the Northwest Ordinances (1787):

The utmost good faith shall always be observed toward the Indians, their lands and property shall never be taken from them without their consent; and in their property, rights, and liberty, they shall never be invaded or disturbed, unless in just and lawful wars authorized by Congress; but laws founded in justice and humanity shall from time to time be made, for preventing wrongs being done to them, and for preserving peace and friendship with them.

Within a few decades this guarantee of legal, political, and property rights was undermined by a series of Supreme Court decisions and the passage of a new federal law.

The rulings in question were written by Chief Justice John Marshall. In Johnson v. M’Intosh (1823), the court ruled that European doctrine gave a “discovering” (e.g., colonial) power and its successors the exclusive right to purchase land from aboriginal nations. This ruling removed control of land transactions from the tribes, which had previously been able to sell to whomever they wished. In Cherokee Nation v. Georgia (1831), the court further opined that the political autonomy of Indigenous polities was inherently reliant on the federal government, defining them as domestic (dependent) nations rather than foreign (independent) nations. This status prevented tribes from invoking a number of privileges reserved to foreign powers, such as suing the United States in the Supreme Court. In a third case, Worcester v. Georgia (1832), the court ruled that only the federal government, not the states, had the right to impose their regulations on Indian land. This created an important precedent through which tribes could, like states, reserve some areas of political autonomy. Together these three decisions suggested that Indigenous nations were simultaneously dependent upon and independent from federal control; subsequent case law has often focused on defining exactly which form of relationship obtains in a particular situation.

Even as these cases made their way through the U.S. courts, Congress was passing the Indian Removal Act (1830). The act was initiated after the 1828 discovery of gold on Cherokee land in Georgia. Speculators hoping to profit from the discovery, including President Andrew Jackson, subsequently pressured Congress to find a way to legally divest the tribe of its land. Jackson’s speech On Indian Removal, presented to Congress in December 1830, provides a sample, although certainly not a full account, of his rationalizations for such action.

The Indian Removal Act enabled the president to designate tracts of land west of the Mississippi as new Indian Territories, to negotiate with tribes to effect their removal from east of the Mississippi, and to fund these transactions and associated transportation costs. The Native American population had not been consulted in these matters and responded in a variety of ways: Black Hawk led the Sauk and Meskwaki in defending their territory; the Cherokee pursued resolution through the courts; the Choctaw agreed to arrange a departure plan with the designated federal authorities; and the Chickasaw gained permission to sell their property and arrange their own transportation to points west. Perhaps the most determined to remain in place were the Seminoles, who fiercely defended their homes; the Seminole Wars (1817–18, 1835–42, and 1855–58) came to be the most expensive military actions undertaken by the U.S. government up to that point.

Ultimately, all the eastern tribes found that overt resistance to removal was met with military force. In the decade after 1830, almost the entire U.S. population of perhaps 100,000 eastern Indians—including nearly every nation from the Northeast and Southeast culture areas—moved westward, whether voluntarily or by force. Encountering great difficulties and losing many people to exposure, starvation, and illness, those who survived this migration named it the Trail of Tears.

The conquest of the western United States

In 1848 the Treaty of Guadalupe Hidalgo granted the United States all of Mexico’s territories north of the Rio Grande (see Mexican-American War); in the same year, gold was discovered in California. Thousands of miners and settlers streamed westward on the Oregon Trail and other routes, crossing over and hunting on Indigenous land without asking leave or paying tribute. From the resident nations’ perspective, these people were trespassers and poachers, although their presence was somewhat ameliorated by the goods and services they purchased from the tribes. Contrary to their frequent portrayal in 20th-century popular culture, few armed conflicts between travelers and Indigenous peoples took place, although tense situations certainly occurred. These circumstances moved the U.S. government to initiate a series of treaties through which to pacify the trans-Mississippi west. Perhaps the most important of these was the First Treaty of Fort Laramie (1851), which was negotiated with the Arapaho, Sahnish, Assiniboine, Blackfoot, Cheyenne, Apsáalooke, Dakota (subset of theOceti Sakowin), Hidatsa, and Mandan nations. Among other issues, it explicitly defined the home territories of each of these peoples, disputes over which had fostered intertribal conflict. It also required the signatory nations to forego battle among themselves and against Euro-Americans and gave the United States the right to build and protect roads through the Plains. In return, the United States agreed to provide a variety of goods and services to the tribes.

Notably, while the impetus for the First Treaty of Fort Laramie was federal concern about the safety of travelers, Indigenous actions against these people paled before the depredations of Euro-Americans, which have been described as genocidal. In the first three decades following the 1848 gold strike, for example, California’s Native American population declined from between 100,000 and 150,000—a figure already depleted by the decades of poor conditions the “novitiates” had experienced at the hands of Spanish missionaries and businessmen—to perhaps 15,000 individuals. In 1850 the California legislature legalized the de facto slavery of Indigenous individuals by allowing Euro-American men to declare them “vagrant” and to bind such “vagrants” by indenture. Thousands of people were enslaved under this statute, and many died of maltreatment. Between 1851 and 1857 the state legislature also authorized some $1.5 million for reimbursement to private individuals who quelled native “hostilities”; most of these private expeditions were little more than shooting sprees and slave raids against peaceful indigenous settlements.

For a time, the conquest of the West was overshadowed by the American Civil War (1861–65). Conflicts in the Plains increased during this period and included two of the worst interethnic atrocities of 19th-century America: the Sioux Uprising (1862), in which Dakota warriors killed some 400 settlers in Minnesota, many of whom were women and children, and the Sand Creek Massacre (1864), in which members of the Colorado militia killed at least 150 and perhaps as many as 500 people, mostly women and children, at a Cheyenne village known to be peaceable.

As the Civil War ended, increasing numbers of U.S. troops were sent to pacify the North American interior. The federal government also began to develop the policies that eventually confined the nations of the West to reservations, and to pursue treaties with Native American polities in order to effect that goal. These agreements generally committed tribes to land cessions, in exchange for which the United States promised to designate specific areas for exclusive Indigenous use and to provide tribes with annual payments (annuities) comprising cash, livestock, supplies, and services. A second major treaty convention occurred at Fort Laramie in 1868, but treaty making ceased with the passage of the Indian Appropriation Act (1871), which declared that “hereafter no Indian nation or tribe” would be recognized “as an independent power with whom the United States may contract by treaty.” Indian affairs were thus brought under the legislative control of the Congress to a much greater extent than previously.

These actions eventually had an enormous effect on Native nations. However, policy changes made from afar are difficult to enforce, and Washington, D.C., was nearly 1,700 miles (2,700 km) away from the communication nexus at Fort Laramie. The tasks of finding, moving, and restricting the nomadic nations to their designated reservations were given to the U.S. military. The best-known event of the conquest of the American West, the Battle of the Little Bighorn (June 25, 1876), arose directly from this delegation of authority. Notably, and despite its notoriety, this engagement caused few or no injuries to noncombatants; only military personnel were directly injured or killed. During the battle a combined group of Cheyenne and Oceti Sakowin warriors defended their families from George Armstrong Custer and the U.S. 7th Cavalry. Custer’s mission had been to remove these people (several hundred in all) to their reservations, and he had intended to forcibly capture or kill every member of the community, including women, children, the aged, and the infirm, in order to do so. With the exception of a small group of soldiers led by Maj. Marcus Reno, who were trapped under fire on a hill, Custer and his troops were completely annihilated. Unfortunately for the western nations, this event—and particularly Elizabeth Custer’s decades-long promotion of her husband’s death as an atrocity, despite his status as a recognized combatant—spawned a prolonged media sensation that reignited the United States’ commitment to complete hegemony over Native America.

By the late 1880s an Indigenous millenarian movement, the Ghost Dance religion, had arrived on the Plains. Growing from an older tradition known as the Round Dance, the new religion was based on the revelations of a young Paiute man, Wovoka, who prophesied the departure of the Euro-Americans and a reunion of Indigenous individuals and their departed kin. The songs and ceremonies born of Wovoka’s revelation swept the Plains, offering hope to Indigenous believers but also shifting over time and space from a pacifist set of practices to one with at least some military aspects. Concerned that the Ghost Dance would disturb the uneasy peace of the northern Plains, U.S. government agents moved to capture its proponents. Among them was the Oceti Sakowin leader Sitting Bull, who was killed on December 15, 1890, while being taken into custody. Just 14 days later the U.S. 7th Cavalry—Custer’s regiment reconstituted—encircled and shelled a peaceful Oceti Sakowin encampment at Wounded Knee, South Dakota, an action many have argued was taken in revenge of the Little Bighorn battle. More than 200 men, women, children, and elders who were waiting to return to their homes were killed. Although this massacre marked the effective end of Native military resistance in the western United States, tribes and individuals continued to resist conquest in a variety of other ways.

The conquest of western Canada

For the Indigenous peoples of the Canadian West, the 19th century was a time of rapid transformation. The fur trade and a variety of large prey animals were in decline, and, with the elimination of government tribute payments, this created a period of economic hardship for the tribes. In addition, Canada’s northern forests and Plains saw an influx of European and Euro-American settlers and a series of treaties that greatly reduced the landholdings of aboriginal peoples.

Many legal issues of import to Indigenous nations were decided early in the century, before Canadian independence. Among the most important of these policies was the Crown Lands Protection Act (1839), which affirmed that aboriginal lands were the property of the crown unless specifically titled to an individual (see crown land). By disallowing Indigenous control of real estate, a requirement for full citizenship in most of Canada, the act disenfranchised most Native peoples. Through the 1850s a series of additional laws codified Indian policy in Canada. Initiated by the assimilationist Bagot Commission (1842–44), these laws defined what constituted Native identity, mandated that individuals carry only one legal status (e.g., aboriginal or citizen), prohibited the sale of alcohol to Native peoples, and shifted the administration of Native affairs from the British Colonial Office to Canada.

For Native peoples, the most momentous legal changes in the later 19th century included the creation of the Dominion of Canada (1867) and the passage of legislation including the Gradual Civilization Act (1857), the Act Providing for the Organisation of the Department of the Secretary of State of Canada and for the Management of Indian and Ordnance Lands (1868), the Manitoba Act (1870), and the first consolidated Indian Act (1876). Events of the 19th century were also heavily influenced by the intensifying competition between the Hudson’s Bay Company and the North West Company, a rivalry with roots a century old.