This uncommon map is from Barlow and Heap's "Letter from the Secretary of War, Accompanying an Engineering Report of a Reconnaissance of the Yellowstone River in 1871." The captains were dispatched by Lieut. General Sheridan to investigate the reports of extraordinary phenomena in the Yellowstone region. They entered the area that would become Yellowstone National Park in July 1871 under the same military escort provided for the Hayden party. After splitting from the main group, the expedition visited Tower Falls, Mount Washburn, the lower and upper falls of the Yellowstone River, Mud Volcano, Yellowstone Lake, and numerous geyser basins. They then proceeded southward to explore the basins of the upper Snake and Yellowstone Rivers, the first detailed exploration of these areas since the 1830s. The map details the routes traveled and locates camp sites with dates. There is detailed topography, watershed and landmarks. Blevins comments that Barlow and Heaps's "map provides the first detail of many areas of the park as the Hayden maps based upon his 1872 survey would not be published until 1873." An important map that should be in any Yellowstone collection. Accompanied by the disbound and complete 43-page report, followed by an unrelated 14-page document concerning arbitration of the Alabama Claims from the Civil War. Housed in archival paper covers.

References: Blevins #225; Wheat #1220.

Condition: B+

The folding map has a hint of toning along the fold lines and an 8" fold separation that has been closed on verso with archival tape. Disbound text is mostly clean and bright.