EARLY GEOLOGIC RECONNAISSANCE OF THE SOUTHWESTERN UNITED STATES BY THE U.S. ARMY CORPS OF TOPOGRAPHICAL ENGINEERS

In the first half of the 19^th century, the U.S. Army Corps of Topographical Engineers made some of the first published contributions to the geological understanding of Western North America. The Corps was formally tasked with exploring the Western Interior of North America as part of the United States territorial expansion. As well as being a military force, the Corps mapped national boundaries, existing roads, mineral resources and worked to improve public works projects. As part of these practical efforts, the members of the Corps were engaged in collecting and communicating scientific information through reports, maps, and illustrations. Comprised solely of officers, the members of the Corps received formal training in mineralogy and geology at West Point and many interacted and corresponded with American and European scientists. Their approaches to characterizing geologic and other scientific information was influenced by the prevailing Romanticism and Humboldtian approaches to science, which emphasized the exotic yet ordered, complex yet interconnected and unified, and regarded an observer’s emotional connection to the objects and method of study as an important element of the scientific process.

Two expeditions during the years that encompass the Mexican-American War included early geologic observations of the southwest. The first was in 1845 led by Lieut. James W. Abert across present-day Colorado, New Mexico, and Oklahoma and a second in 1846-47 from Missouri to California led by Lieut. Col. William H. Emory. Geologic observations included topography, rock descriptions, river conditions and sediment, and remarks on fossil remains and mineral resources. Accompanying lithograph prints and illustrations demonstrate field and structural relationships of rock strata. Their concerns focused on practical and logistical applications of geomorphology, minerals and rock characteristics, and mineral resources. Such early reconnaissance of the West by the Corps of Topographical Engineers made the new frontier accessible as well as provided a fundamental, local geologic knowledge for later, more specialized, academic observers, in which to cultivate the broader implications of geometric/structural relationships, time/stratigraphic correlations, and geologic mapping.