Indians of a highly developed civilization lived throughout Moapa Valley from 300-1100 A.D. Several hundred ancient pithouses, campsites, rockshelters, salt mines and caves of Anasazi people make up what is commonly known as "Lost City." These people cultivated corn, beans and squash in fields irrigated by river water. They also gathered wild seeds and fruits and hunted widely for deer, antelope, desert bighorn sheep, small mammals and birds. They wove fine cotton cloth, fired beautifully painted and textured pottery and mined and traded salt and turquoise to coastal tribes for seashells. Early dwellings were circular pithouses below ground; later dwellings above ground were single-story adobes having up to 100 rooms.

Lake Mead, created by Hoover Dam, flooded the most intensively developed portion of Lost City.