Established in 1906, Mesa Verde National Park is a major site of prehistoric cliff dwellings and open pueblos of the Anasazi Indians. Ruins and artifacts document about 1,000 years of culture. Most impressive of the ruins is the Cliff Palace, which was excavated in 1909. Dating from about the 12th century, it contained more than 200 rooms and 23 ceremonial chambers. After about 1300 A.D., the inhabitants of Mesa Verde abandoned their villages and moved, either because of raids by other peoples or extreme drought. The cliff dwellings were forgotten until the end of the last century, when they were discovered by cowboys and subsequently excavated.