One of the last Army expeditions in the region, this was an exploration of parts of New Mexico, Utah, and Colorado during the summer of 1859, northward out of Santa Fe along the Old Spanish Trail, to discover if there were a practical railroad or wagon route through the San Juan River country to the southern settlements of Utah Territory (in case of further armed conflicts like the "Utah War"), and on to the west coast. The report found the mountainous terrain impractical for a railroad, and the weather too severe for permanent settlement. The Civil War delayed publication.

At head of title: Engineer Department, U.S. Army. Includes index.

General report /[by J.N. Macomb] -- Geological report / by J.S. Newberry -- Descriptions of Cretaceous fossils / by F.B. Meek -- Descriptions of Carboniferous and Triassic fossils / by J.S. Newberry.