Mount Graham International Observatory

Mount Graham International Observatory is a division of Steward Observatory, the research arm of the Department of Astronomy at the University of Arizona. It stands in the Pinaleño Mountains of south-eastern Arizona, near Mount Graham and west of Safford, and was called the Columbus Project during development. Construction began in 1989. It operates and maintains facilities for three scientific organisations: the Vatican Advanced Technology Telescope and the Heinrich Hertz Submillimeter Telescope, both of which began operating in 1993, and the Large Binocular Telescope, which began work with its mirrors used independently in 2004 and jointly from 2008. Public tours are run by the Discovery Park Campus of Eastern Arizona College between mid-April and mid-October, subject to weather and to reservation. The construction and presence of the structures remain contested by environmentalists, University of Arizona students and Indigenous tribes: they stand on ground sacred to and ancestrally used by Western Apache peoples, and the San Carlos Apache Tribal Council approved formal opposition to the telescopes. The environmentalist objection centred on the endemic Mount Graham red squirrel.

Where it is

Mount Graham International Observatory is a observatory near Safford, in Graham County. It is one of the observatories in this database, and appears in the statewide ranking of Arizona attractions.

How this ranking was reached

No official visitor count is published for Mount Graham International Observatory, so its score rests on public interest and tourism significance, and is capped below the level a measured attraction can reach. That is why the medium confidence above is not higher. The weighting is explained in full on the methodology page, and every axis is broken out under Facts and sources at the foot of this page.

Note on the data: No official visitor count is published for this attraction.

Mentioned in

• Arizona protects its night sky in one set of places and uses it in another — Eight Arizona attractions hold International Dark Sky Park status and all eight publish visitor counts; twelve working observatories publish none.

Sources

• Public interest: Wikimedia pageviews (en.wikipedia, human traffic), 2024
• Coordinates and designations: Wikivoyage(opens in a new tab)
• County: U.S. Census geography via FCC Area API, resolved from coordinates
• Official site: http://www.eac.edu/discoverypark/mgio.shtm(opens in a new tab)

Record last verified 2026-08-12.