Winchell, N. H. (Newton Horace), 1839-1914At head of title: Geological and Natural History Survey of Minnesota.; Relief shown by hachures.; Includes inset: Map of the silver mining region, Thunder Bay District, Canada.on sheet 87 x 122 CentimetersJPEGUMN_ALMA:9915454670001701engpublisher not identified (United States)PublicGeological map of the iron regions of MinnesotaMapsMinnesotaUniversity of Minnesota