37 x 50 cm. Prime meridian: Washington, D.C. Relief shown by hachures and spot heights. "Issued May 7th, 1877. 2nd ed., June 30th, 1881." "Atlas sheet no. 77(B)." "Expeditions of 1871 & 1786 under the command of 1st. Lieut. Geo. M. Wheeler, Corps of Engineers, U.S. Army." "Weyss, Herman & Lang, del." 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. Geological map. "Prof. John J. Stevenson, geological assistant." Original publisher: U.S. Geographical Surveys West of the 100th Meridian, Scale: 1 inch to 4 miles or 1: 253440.