Canyon de Chelly National Monument was established on April 1, 1931 as a unit of the National Park Service. It is located in northeastern Arizona within the boundaries of the Navajo Nation. It preserves ruins of the early indigenous tribes that lived in the area, including the Ancient Pueblo Peoples (also called Anasazi) and Navajo. The monument covers 131 square miles (339 km) and encompasses the floors and rims of the three major canyons: de Chelly, del Muerto, and Monument.