The Four Corners Monument marks the quadripoint in the Southwestern United States where the states of Arizona, Colorado, New Mexico and Utah meet. It is the only point in the United States shared by four states, leading to this area being called the Four Corners region. The monument also marks the boundary between two semi-autonomous native American governments, the Navajo Nation, which maintains the monument as a tourist attraction, and the Ute Mountain Ute Tribe Reservation.
The origins of the state boundaries marked by the monument occurred during the American Civil War, when the United States Congress acted to form governments in the area to combat Confederate ambitions for the region. Claims are sometimes made that the monument was misplaced in the initial surveys. The accuracy of the surveys has been defended by the U.S. National Geodetic Survey and the monument has been legally established as the corner of the four states.http://www.navajonationparks.org/htm/fourcorners.htm