Geological map of Wisconsin, Iowa and Minnesota : exhibiting, also, the extension of the Iowa coal-field into Missouri, and its relation to the Illinois coal-field / constructed from observations by the United States Geological Corps, under instructions from the Secretary of the Treasury, by David Dale Owen ; middle, northern and northeastern Minnesota by J.G. Norwood ; the greater part of the southern shore of Lake Superior, in Wisconsin, by Col. Chas. Whittlesey. 1851. Engraved by W. Smith. Washn. (to accompany) Illustrations to the Geological Report of Wisconsin, Iowa, and Minnesota. (with) Report of a Geological Survey of Wisconsin, Iowa and Minnesota ... 1852. Inset: Geological map of the north shore of Lake Superior : on the scale of the original m.s. map. Scale [ca. 1:600,000].
