Task: Question Answering
Input (English): Passage: In the years following the Ancestral Puebloan's departure from Chaco Canyon, several migrations to the region occurred. During the 15th century, Navajo people emigrated to the area from northwestern Canada, and in the 18th century Spanish explorers and settlers came from the south. The Spanish investigated parts of the San Juan Basin, but there is no record of them ever finding Chaco Canyon. When cartographer Bernardo de Miera y Pacheco drew a map in 1774 of Spanish land holdings in the region, he labeled Chaco Canyon with the word Chaca, but it is unlikely he ever visited the area. In 1823 the governor of New Mexico, José Antonio Vizcarra, discovered ancient ruins in the canyon during a military campaign against the Navajo. Vizcarra's account is the first historical record of the Chacoan great houses that were "of such antiquity that their inhabitants were not known to Europeans". In 1844, Josiah Gregg made the first published reference to Chaco Canyon in his popular book, Commerce of the Prairies.
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. Simpson was impressed by Chetro Ketl's masonry, which he described as "a combination of science and art which can only be referred to a higher stage of civilization and refinement than is discoverable in the works of Mexicans or Pueblos of the present day." Simpson and company documented their findings, noting the location and style of the great houses, taking measurements, and sketching the canyon's major ruins. They described the kivas as "circular apartments sunk in the ground". Simpson briefly explored Chetro Ketl, documenting six of its round rooms and 124 rooms on the ground floor of the four-story building. He noted an especially well preserved room where "the stone walls still have their plaster upon them in a tolerable state of preservation." Vivian credits Simpson's 1850 report detailing their brief exploration of the canyon and Richard H. Kern's lithographs as the beginning of Chacoan archeology. The scientific investigation of Chaco Canyon started when Richard Wetherill began his exploration of the canyon in 1895. Wetherill was well known for his discovery of some of the largest Ancestral Puebloan dwellings in Mesa Verde, and after an invitation from amateur archeologist Sidney Palmer to survey Chaco Canyon, organized a one-month expedition to the region. He secured financial backing for a full season soon afterward, and in 1896 full-scale excavations began at Pueblo Bonito. 
Question: What is the last name of the explorer who found an especially well preserved room in Chetro Ketl?
Output (English): Simpson.