 The United States started exploring the region following the Mexican–American War of 1846–48 and the acquisition of the New Mexico Territory.During a military campaign against the Navajo in 1849, Lieutenant James Simpson of the United States Army Corps of Engineers became interested in the canyon's ruins.A group led by the governor of Jemez Pueblo, Francisco Hosta, explored the canyon; its members included Simpson and the brothers Richard and Edward Kern, who were respectively an artist and a cartographer.