They developed a long trading relationship with French trappers and colonists.Throughout the Red River of the North area, French trappers married Native American women, and their descendants continued to hunt and trap.Between 18, eleven new counties were created from Pembina, including Cass County and Grand Forks County.Pembina took its current form in 1887, when Cavalier County was increased in size.The prairies’ rivers and lakes which extend to the height of land of the Mississippi, and the immense plains which feed innumerable herds of bison to the westward and from which the Chippewa and half breeds [Métis] of this region obtain their subsistence, contains within their limits a country about 400 miles from north to south and more than five hundred miles from east to west." The Métis used two-wheeled, ox-drawn carts to transport great quantities of furs to market along the Red River Trails, between what is now Winnipeg, Canada and Mendota or St. They also used the ox-carts to transport food and shelter during extended buffalo hunts.Over time, the Ojibwe were persuaded to cede much of their land by treaty to the US, which in turn sold it to homesteaders.
Father George Belcourt, a Catholic Jesuit missionary who served them, described their territory in 1849 as the following: "We understand here, that the district or department called Pembina, comprises all of the country or basin which is irrigated or traversed by the tributaries of the Red River, south of the line of the 49th parallel of latitude.
The Chippewa pushed the Lakota to the west and became dominant in the area.
The county was created by the 1866–1867 Dakota territorial legislature, and was organized on August 12, 1867.
A large mixed-race population developed, recognized as an ethnic First Nations group in Canada called the Métis.
The Ojibwe and Métis generally supported the French forces during the Seven Years' War in the mid-eighteenth century against Great Britain.