Cliff dwellers, prehistoric Native American people who built elaborate houses, some with hundreds of rooms, sheltered beneath overhanging cliffs in the southwestern United States. The earliest of these multistoried dwellings dates from about A.D. 1000. They were a peaceful agricultural people whose inaccessible communities protected them from roving tribes such as the Apaches. In the 16th century the Spanish found the settlements mysteriously abandoned. Archeologists classify the cliff dwellers as members of the pueblo culture, ancestors of the tribes that built the large pueblo villages on the plains. The ruins of the cliff dwellings, well preserved in the dry desert climate, are found in Mesa Verde National Park, Colo., and in national monuments in Arizona, New Mexico, and Utah.