1. Minnesota transportation map : Highways, railroads, canals, air lanes, and dredged channels Maps University Of Minnesota Public content 1940. United States. Public Roads Administration. Cartographic Details: Scale 1:250,000. approximately 1 in. to 4 miles ; Modified polyconic projection (W 97‚Å∞15 π--W 89‚Å∞30 π/N 49‚Å∞22 π--N 43‚Å... The Survey (Washington D.C.).