 Sibley was a partner in the American Fur Company, and considerable fur trade occurred at Mendota due to the accessibility of the confluence.Ongoing United States expansion into the then "Northwest Territory" led to government purchase of land from the Dakota people (the Mdewakanton, Wahpekute, Wahpeton, and Sisseton bands) via the Treaty of St. Peters and the Treaty of Traverse des Sioux in 1851. and the Treaty of Mendota.After the Minnesota Territory was established in 1849, Dakotah County (later Dakota County) spanned from the Mississippi River to the Missouri River.