Following the early explorers and traders, movement by Euro-Americans into the northern plains began to increase. In 1851, the U.S. government signed a treatyAn agreement between the U.S. government and an American Indian tribe with several American Indian tribes, including the Dakota Sioux. Part of the treaty stated that travelers would not pass through the tribal lands.
It did not take long before the U.S. government broke the treaty. Settlers,People who came to an area to live there or people who moved into an area to stay, were pouring into Minnesota, and land was being taken away from the tribes. This caused tensions between the settlers and the Indians.
Minnesota Territory was organized in 1849. This territory included the part of North Dakota east of the Missouri River. In 1858, Minnesota became a state, but the part of North Dakota between the Missouri River and the Red River was not organized into any territory for almost three years. Dakota Territory was formed in 1861. It included all of North Dakota, all of South Dakota, most of Montana, and most of Wyoming. In 1868, Dakota Territory was reduced to just North Dakota and South Dakota. Twenty‐one years later, on November 2, 1889, North Dakota and South Dakota became states.