James Hervey Simpson and the first record of San Juan Basin geology
— Barry S. Kues

James H. Simpson, a lieutenant in the Army Corps of Topographical Engineers, reported the first extensive geological observations of the San Juan Basin while accompanying the Washington Expedition against the Navajos in 1849. Simpson's record of this expedition also includes the first American descriptions of the Jemez Springs area, the ruins at Chaco Canyon, Canyon de Chelly, and Inscription Rock (El Mono), as well as much information on the Hispanic, Pueblo and Navajo inhabitants of New Mexico shortly after it came under American control. He also named Washington Pass, in the southern Chuska Mountains, and Mount Taylor. This paper summarizes the day-to-day progress of the expedition, and discusses Simpson's geological observations and interpretations along the route in the light of present knowledge of the geology of this area.