Early geological explorations in northeastern and east-central New Mexico
— Barry S. Kues

When General Stephen W. Kearny and his Army of the West entered Santa Fe on 18 August 1846, establishing American jurisdiction over New Mexico, virtually nothing was known of the geology of this vast territory. Although mining on a small scale had been practiced for centuries, there is no evidence of any scientific effort to understand the geological history of any part of New Mexico during the Spanish and Mexican periods. The geography of some parts of the territory, especially the relatively populated region along the Rio Grande, was reasonably well known, but large areas were terra incognita to Americans and Mexicans alike. Information about the land and people of New Mexico available to the entering Americans had been gleaned largely from the sometimes romanticized accounts of travellers and traders, a few American residents and occasional American exploring parties that inadvertently or by design had penetrated New Mexico against the wishes of its Spanish, then Mexican, administrations.

Establishment of American control in New Mexico produced an immediate requirement for additional information, not only concerning the agriculture, industries and lifestyles of the Hispanic and Indian residents, but also about the roads, mineral resources, topography, climate, fauna, flora and geology of the territory. Such information was essential to the proper administration of the territory and, against a complex tapestry of abrupt, forced and sometimes antagonistic integration of Hispanic, Indian and Anglo cultures, the United States Government mounted a concerted effort to acquire it.

The growth in knowledge of the geology of New Mexico during the first decade of American administration was explosive. Although many of the observations made during this time were preliminary, generalized and in some instances erroneous, the efforts of the military men, naturalists and geologists who first examined and reported upon New Mexico's rock record represented an important first step in the understanding of New Mexico's geology. In this paper, observations and interpretations of the geology of the northeastern quadrant of New Mexico made through the first decade of American administration of the territory (Fig. 1) are described, together with some of the circumstances and consequences of these efforts. The richest sources of information about these early geological studies and the men who conducted them are their published journals and papers, and I have quoted liberally from them. A modern synthesis of the work of the U.S. Army Corps of Topographical Engineers is the excellent book by Goetzmann (1959), which I have utilized extensively in this account. Early descriptions of the geology of one important area in east-central New Mexico—the Tucumcari Mountain area—are touched on but lightly here; a companion paper in this guidebook (Kues, 1985) summarizes in detail the development of our knowledge of the geology of that area.