39 x 52 cm. Relief shown by hachures and spot heights "Issued June 30, 1881." "Expeditions of 1873, 1878 and 1879 under the command of 1st. Lieut. Geo. M. Wheeler, Corps of Engineers U.S. Army." Geological map Probably originally published as part of the geological atlas which is an appendix to the Surveys' Report upon United States geographical surveys west of the one hundredth meridian. "Prof. John J. Stevenson, geological assistant." "By order of the honorable the Secretary of War under the direction of Brig. General A. A. Hunphreys, Chief of Engineers, U. S. Army." Original publisher: U.S. Geographical Surveys West of the 100th Meridian, Scale: 1 inch to 4 miles or 1: 253440.