Expedition to the Southwest: An 1845 Reconnaissance of Colorado, New Mexico, Texas, and Oklahoma

Lieutenant James William Abert (1820-97) of the United States Army Topographical Engineers received orders in 1845 to explore the Canadian River region of the southern plains-an area covering present-day Colorado, New Mexico, Texas, and Oklahoma. Although this land was still in Mexican territory, the United States had gradually abandoned most of the diplomatic niceties regarding its boundaries with Mexico by that time.

Abert set out from Bent's Fort to conduct a detailed reconnaissance. He...