39 x 50 cm. Relief shown by hachures and spot heights. "Issued May 7th 1877-2nd ed. June 30th, 1881." "Expeditions of 1878 and 1879 under the command of 1st. Lieut. Geo. M. Wheeler, Corp. of Engineers U.S. Army." "Weyss Herman & Lang Del." Prime meridians: Washington, D.C. and Greenwich 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.