A literal and spiritual sandstone cathedral, Canyon de Chelly is one of the more unique national monuments in the United States. While it was added to the National Park System in 1931 by President Herbert Hoover, the agreement left most of the landscape as the property of the Navajo Nation. To this day, the monument is managed through a partnership between the National Park Service and the Navajo Nation, and it serves to sustain the living Navajo community.