The Navajo tribe is one of the largest Native American tribes in the United States with over 250,000 members living in its reservation area. The Navajo reservation is approximately 27,000 square miles and extends into four states. During World War II, Navajo soldiers developed the Navajo Code for the U.S. campaign in Iwo Jima.
Another of the original Native American tribes in the Southwest United States is the Hopi, who live on three mesas -- natural plateau structure -- in northern Arizona. The oldest continually habited Hopi village is Old Oraibi, which dates back to A.D. 1050. The Hopi's spiritual life revolves around kachina, or the spiritual life forces of the Hopi.