Trade Before the Civil War
Rhoda and Carolyn Gilman and Deborah Schultz, Red River Trails: Oxcarts Between St. Paul and the Selkirk Settlement, 1820-1870 (1979) -- an excellent account of the oxcart trade between Fort Snelling (and later St. Paul) and the early settlements in southern Manitoba.
William Lass, A History of Steamboating on the Upper Missouri River (1962) -- although concerned with the lands west of Minnesota, this account of these areas is important to understanding early trade development in Minnesota.
George B. Merrick, Old Times on the Upper Mississippi: The Recollections of a Steamboat Pilot from 1854 to 1863 (1987) -- a well written memoir of a riverboat pilot who traversed the Mississippi and Minnesota rivers; contains some nice descriptions of early Minnesota towns, including Minneapolis.