Large format map of Kansas, Nebraska, Dakota and part Colorado and Wyoming, extending as far southeast as Denver, Colorado City and St. Vrains. Excellent detail of railroads including the Union Pacific, showing two parallel routes one ending in Denver the other a little north and heading into Wyoming and off the map. Dozens of forts located. Numerous routes of explorations and surveys are drawn in. Areas roamed by principal Indian Tribes are shown. Warren's extensive knowledge of the area and his skill as a cartographer are obvious in this large, detail-filled map. Geology of eight different groups is indicated by hand coloring. Geology was provide by Dr. Ferdinand Hayden, then Professor of Geology and Mineralogy at the University of Pennsylvania, and only 4 years prior to his famous trip of exploration into Yellowstone that resulted in Yellowstone becoming the first National Park in the United States. The map accompanied Hayden's Final Report of the United States Geological Survey of Nebraska and Portions of the Adjacent Territories, (42d Congress 1St Session House of Representatives Ex. Doc. No. 19), published in 1872. Linen backed, with a bit of loss along a few folds, but generally an excellent example of this remarkable map, which rarely appears on the market.