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. Reflecting one of the longest continuously inhabited landscapes of North America, 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 83,840 acres (131.0 sq mi; 339.3 km2) and encompasses the floors and rims of the three major canyons: de Chelly, del Muerto, and Monument. These canyons were cut by streams with headwaters in the Chuska mountains just to the east of the monument. None of the land is federally owned. In 2009 Canyon de Chelly National Monument was recognized as one of the most-visited national monuments in the United States.