From Lakota America: A New History of Indigenous Power, by Pekka Hämäläinen (The Lamar Series in Western History; Yale U. Press, 2019), Kindle pp. 47-49, 83:
The long struggle for allies, trade, and relevance had been spearheaded by the four Dakota [council] fires, the Mdewakantons, Sissetons, Wahpetons, and Wahpekutes. They had played a key role in the birth of the all-important Sauteur [Ojibwe] alliance and in nurturing the relationship with the French, and their lands around Mde Wakan [Mille Lacs Lake] were the place where most foreigners sought access to the Sioux. To the outsiders they seemed “the masters of other Scioux.” But the long struggle involved all seven fires. No oyáte [‘people, tribe’] or thióšpaye [‘local band’] was immune to the seemingly endless blows or denied the rewards when they finally came.
Distance shielded the Lakotas, the westernmost Sioux division, against the hardest blows—the massacres, the repeated border conflicts, the exasperating indifference of French traders. They remained a shadowy, enigmatic people to the French, who caught only glimpses of them. They were “Nations Tintonha,” “The Inhabitants of the Meadows,” who lived in the West “certain Seasons of the Year.” Eventually, to facilitate deepening western excursions, growing numbers of Lakotas moved permanently west of the Mississippi. By the late 1690s the French knew the lands around the upper Minnesota Valley as the Lakota domain—“Pays et Nations des Tintons”—and few years later Le Sueur was struck by the geographical and cultural distance that separated Lakotas from their eastern kin: they did not gather wild rice or use canoes, and they kept to “the prairies between the Upper Mississippi and the river of the Missouris” where they had no fixed villages.
What to the French seemed a Lakota detachment from the eastern Sioux was actually a part of a larger strategy of fueling the growing fur trade. When the trade took off, Sioux needed large quantities of castor: one gun cost approximately ten skins of winter beaver, and the thousands of Sioux warriors needed thousands of guns. The greatest castor reserves lay to the west, in lands still beyond the fur trade’s long tentacles but within Lakotas’ reach. Each fall Lakota bands left for the western prairies beyond the forest line, spending months in scouring the rivers and streams for thickly furred beavers and living in light deerskin lodges. While there, they lived off the bison, which seemed to grow more abundant with distance, and clashed with the resident hunter-farming peoples who saw them as invaders. Already in the late 1680s the the Arikara Indians on the Missouri River—more than two hundred miles west of the Lakota domain—seem to have been engaged in grueling wars with the westering Lakotas.
By the turn of the century the Lakotas were a growing and often violent presence on the tall-grass prairies west of the Minnesota River. But they were sojourners, not conquerors. They were in the West, but the West was not theirs. Each spring they returned east to the precious prairie-forest ecotone where they could enjoy one of the best diets on the continent. There, they reconnected with their kin, traded skins for iron, shared the calumet, and reaffirmed their place in the world as one of the Seven Council Fires. Sicangu Lakotas came together with their kin every seven years to make offerings to Wakȟáŋ Tȟáŋka, Great Spirit, and reaffirm their interconnectedness.
Lakotas were suspended between western promises and eastern realities. Their firsthand experience of the new world of Indians and Europeans was limited, but they knew its challenges and opportunities intimately through their eastern relatives whose sufferings and successes were theirs. They knew what not having allies or guns meant, and they had learned that people were capable of astonishing violence to secure them. They knew that the world had changed irrevocably and that no one could ignore the European newcomers and their wašíčuŋ [superhumans]. And they knew that this new world was an unforgiving place where people often were expiring if they were not expanding.
When Lakotas finally pushed into the West in the early eighteenth century, drawn by its tremendous possibilities, they carried with them a specific set of convictions about the world. They would have to adapt to new western realities, but so too would the West have to adjust to theirs.
By the mid-eighteenth century the Sioux had shifted shape many times over. They had opened their lands and villages for real and potential allies—Sauteurs [Ojibwe], Cheyennes, Mesquakies [Fox], Frenchmen, and many others—while contending with numerous rivals as they struggled to find a place in the rapidly changing world. They had reached out to Onontio [‘Great Mountain’, the French colonial governor] far in the East—Sioux visits to Montreal had become almost commonplace—while expanding aggressively in the West. The boundary of the four Dakota oyátes shifted gradually west and south from Mde Wakan as bands sought safety from violence and trade along the Mississippi and Minnesota Rivers; Lakotas expanded their domain all the way to the Mníšoše [Missouri R.] in search of beaver, bison, horses, and captives. Along the way they pushed aside the Iowas, Otoes, Omahas, and Poncas, turning the prairies into a shatter belt of displacement and destruction—a western version of the mid-seventeenth-century Iroquois shatter zone in the Great Lakes. As Lakotas gradually took over the vacated lands, they turned the Očhéthi Šakówiŋ [Seven Council Fires] into a territorial giant that commanded nearly one hundred thousand square miles of land—the second largest Indigenous domain in North America after the rising Comanche empire in the southern Great Plains.