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What we do International Dark Sky Places

Greater Big Bend International Dark Sky Reserve

Milky Way above Davis Mountains
The Milky Way sets behind Mount Livermore, the tallest peak in the Nature Conservancy's Davis Mountains Preserve. Photo credit: Stephen Hummel.


At over 9 million acres, the Greater Big Bend International Dark Sky Reserve is currently the world’s largest Reserve and protected Dark Sky Place. The Reserve spans from Fort Davis, Texas, to the Rio Grande River at the US/Mexico international border, and includes three protected areas in Mexico – Maderas del Carmen, Ocampo, and Cañón de Santa Elena – making it the world’s first bi-national International Dark Sky Reserve. The protected landscape encompasses a vast area of the Chihuahuan Desert characterized by diverse desert habitat and wildlife, complex geology, and a rich human history. Significant cultural and natural resources dot the landscape of the Reserve representing thousands of years of human occupation and lifeways specially adapted to the rugged desert environment.

The Reserve’s core area is home to the McDonald Observatory, a world-class astronomical observatory and research facility, and the Nature Conservancy’s Davis Mountains Preserve, a 33,000-acre area protected for its ‘sky island’ habitat. The Reserve’s periphery includes two existing International Dark Sky Parks – Big Bend National Park and the Big Bend Ranch State Park Complex – and one International Dark Sky Sanctuary – Black Gap Wildlife Management Area. Long-standing partnerships between the McDonald Observatory, the National and State parks, conservation organizations, advocacy groups, and enthusiastic communities focused on environmental conservation have made the Reserve effort possible. These individuals and organizations have spent countless hours updating outdoor lighting ordinances; collecting and compiling sky quality data; inventorying, documenting, improving lighting; and educating the public about the importance of dark sky preservation. These efforts led to the successful development of the Reserve and will continue to ensure night sky preservation in the Big Bend region into the future.




International Dark Sky Reserve


McDonald Observatory
3640 Dark Sky Dr
Fort Davis, Texas, US 79734
Google Maps


Stephen Hummel, Dark Skies Coordinator
Tel.: +1432-426-4170

Land Area

38850 km2

Social Media

McDonald Observatory (Facebook, Twitter, Instagram)
The Nature Conservancy (Facebook, Instagram)


Press Release
Annual Reports