Apache Point Observatory (APO) is an observatory located at an altitude of 2,780 meters in the Sacramento Mountains, near Sunspot, New Mexico. It is privately owned and operated by the Astrophysical Research Consortium, whose members include New Mexico State University, the University of Washington, the University of Chicago, Princeton University, and Washington State University. APO houses a 3.5-meter (138-inch) telescope for both optical and infrared observations, the 2.5-meter Sloan Digital Sky Survey Telescope, and two smaller telescopes. The observatory opened in 1990.