The Cree controlled two vital resources necessary to the European trading companies—furs and to a lesser degree, fresh meat and pemmican. Their alliances with other tribes (notably Ojibway and Assiniboine) enabled them to expand rapidly into new territory, becoming the dominant group on the Saskatchewan plains. When the treaty commissioners arrived in the 1870s, the Cree were able to gain several significant concessions: increased annuity payments, promise of agricultural assistance, and the supply of a "medicine chest" for medical aid. Forced to live on reserves after the buffalo became extinct, they accepted farming and ranching while retaining their culture, language and identity. Opposing the Cree was the equally powerful Blackfoot Confederacy centred on the Red Deer, Bow and Old Man river systems of Alberta.

The most militant and feared of the Canadian plains Indians were the Blackfoot tribes comprised of the Blackfeet (Siksika), Blood (Kainai), and Peigan (Pekuni). Each tribe had its own chiefs and societies, but they united for some religious ceremonies, intermarried, and hunted or staged horse raids together. They did not become major participants in the fur trade economy until the early 19th century. In the north they supplied the HBC with buffalo dried pemmican, and in the south, they provided the American Fur Company with pemmican and buffalo robes. When the buffalo economy collapsed in the 1870s, the Blackfoot people became destitute within just three years of signing Treaty No. 7. The Siksika settled on their reserve at Blackfoot Crossing on the Bow river; the Bloods selected their reserve between the Belly and Old Man rivers in 1883 where over 3,000 members settled; the Peigan established their reserve near the Bloods on the Old Man River near Pincher Creek. A number of Blackfoot people became successful farmers and ranchers, but since World War 11, the limited amount of reserve land and the rising population has forced hundreds to seek work and housing in nearby urban centres.

The cross-cultural contacts resulting from the expansion of the fur trade onto the western plains significantly altered the Indians' way of life. The European traders—first the English, through the Hudson's Bay Company, and then the French-Canadian voyageurs, and later the North West Company (to 1821) became welcomed visitors to Indian territory. The Cree around James Bay initially dominated the fur trade in their role as "Homeguard Indians." The HBC built its trading posts around the river outlets along the Hudson's Bay coastline, and sent in the occasional explorer such as Henry Kelsey in 1690 and then Anthony Henday in 1754 to report on the unexplored "Indian Territory".

The Indians became equal partners in the fur trade economy. Both parties benefited from their mutual trade activities, the posts becoming centres of commercial and social activity. Indian families and bands brought furs and fresh meat to exchange for trade goods. They gradually adopted more of the white man's food, clothing, and technology, becoming less self-sufficient and instead of producing for their own tribal needs, they now supplied the growing European fur market. The Cree, in particular, enjoyed an unprecedented growth in power and influence as middlemen in the fur trade network. They pushed aside other tribes such as the Sioux. On the Plains they formed alliances with the Ojibway and Assiniboine. They readily adopted weapons that offered more security against starvation, protection from enemies, and a means to obtain luxury trade items. The fur trade had a great impact upon Indian society and on their material culture. The gun replaced the bow and arrow; metal utensils replaced bone, wood, stone and leather artifacts; the kettle augmented pottery; European clothing was preferred to hides; beads were used with seeds, quills and feathers; and manufactured goods augmented traditional foods. By the turn of the 18th century, several bands in northern Manitoba were referred to as "post Indians" largely dependent on the HBC for their needs. Also, the hundreds of European traders gave rise to a new aboriginal race of people—the Métis.

The prairie Indians relied primarily on the plains bison or buffalo which numbered in the tens of millions. Although antelope, deer, elk, and fur bearing animals were alternative sources of sustenance, the buffalo hunt was the most spectacular tribal activity. They captured the buffalo during the summer in communal hunts, using buffalo pounds (or corrals) or by driving them over steep cliffs (buffalo jumps). Hunters also stalked the buffalo in wolf skins and on horseback. The buffalo provided a year round food source. Delicacies such as buffalo tongues were required for religious feasts such as the Sun Dance. During the height of the fur trade in the 19th century, buffalo meat was, dried and mixed with tallow and berries to make pemmican for the fur trade companies. The pemmican trade, and later the, sale of hides for industrial use, led to the buffalo's over-exploitation by mid-century. By the early 1880s the plains bison was extinct. The Indians north of the 49th parallel now called on the Queen's representatives to honour their commitments of economic assistance as promised in the treaties.

Treaties between the Indian Nations and the British in eastern Canada before Confederation in 1867 set the precedent for the "numbered" treaties of the 1870s. Beginning with Treaty No. I in 1871 covering southern Manitoba and concluding with Treaty No. 7 in 1877 covering southern Alberta, the federal government obtained legal land cessations in return for various "treaty rights." Indian reserve lands were set aside under Crown trust. Using a formula of one square mile for a family of five (or 128 acres per capita), the government surveyed the reserves. Indian leaders were promised agricultural assistance and economic aid; some were provided an ammunition allowance and fishing twine; schools were built and teachers provided by the department of Indian Affairs in cooperation with the Anglican, Methodist and Roman Catholic churches. The promise of a "medicine chest" in Treaty 6 has been interpreted as meaning free medicare but not free medical facilities.

The many treaty negotiations, each lasting several days and requiring sophisticated language interpretation, have resulted in many legal cases over the years involving land claims. Many of the English concepts with respect to land ownership and legal terminology used in the treaties were not readily translatable into native tongues, giving rise to conflicting claims over the ownership of natural resources. The government has consistently viewed the treaties as final land extinguishments whereas Indian Nations have traditionally argued that they only agreed to share the surface soil and never intentionally surrendered the other resources now under provincial jurisdiction. To the European immigrants, land was a commodity for sale, exploitation or individual possession; to the Indian, land was the source of all life. The air, the sun, the water, and the soil could not be selfishly owned and therefore could never be sold or "surrendered" to the European. Nevertheless, the "White man's law" took effect when the plains tribes took up their reserve lands under the Indian Act, first consolidated in 1876 and still in force today.