Kitt Peak National Observatory (KPNO), part of the National Optical Astronomy Observatory (NOAO), supports the most diverse collection of astronomical observatories on Earth for nighttime optical and infrared astronomy and daytime study of the Sun. Sharing the mountaintop site with the National Solar Observatory, KPNO, founded in 1958, operates three major nighttime telescopes and hosts the facilities of consortia which operate 22 optical telescopes and two radio telescopes. (See the Tenant Observatories list.) Kitt Peak is located 56 miles southwest of Tucson, AZ, in the Schuk Toak District on the Tohono O'odham Nation and has a Visitor Center open daily to the public.