A 2.8 million acre section of the Sonoran Desert was set aside for the Tohono O’odham Nation after the Gadsden Purchase in 1853. The reservation, second largest in America, is home for about 28,000 tribal members, as well as a handful of popular sites, including casinos, the Mission Xavier del Bac, and the Kitt Peak Observatory. A small 200 acre portion of the reservation, in the Quinlan Mountains, is set-up by permanent lease to the National Optical Astronomy Observatory (NOAO) at Kitt Peak. Here in the clear air of southern Arizona astronomers have access to the world's largest assortment of astronomical observation equipment. A three year search studied over 150 possible sites in the United States, and selected the Sonoran Desert area because of the quality of its night skies. Built in 1958, the observatory has enjoyed over 50 years of noteworthy discoveries.
   For astronomy buffs, Kitt Peak National Observatory is open for tours and features 23 telescopes. The McMath-Pierce Solar Telescope is one of the largest in the world, and is unobstructed with a secondary mirror. The 4 meter Mayall Telescope, named for the former director, is one of the most prominent features near the 6875 foot summit and can be seen in Tucson some 45 miles away. Standing 18 stories high, Kitt Peak's main dome and its 158 inch scope weigh in over 500 tons. The huge telescope is primariy used to study faint visible light which is found at the limits of the universe, offering distant views that look back through time.

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