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BLM > Arizona > What We Do > Cultural & Historic Resources > Harquahala Smithsonian Observatory
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Harquahala Smithsonian Observatory

Trail Map (pdf)

photo courtesy of the SmithonianGENERAL INFORMATION: Harquahala Peak Observatory was built in 1920 by the Smithsonian Astrophysical Observatory to measure and record solar activity. Although deserted now, from 1920-1925 a hardy group of scientists lived and worked atop the highest mountain in southwestern Arizona (5681 foot elevation). At the time, it was about an hour's drive from Wenden, Arizona, to the mountain, with a 3-hour hike to the top of the peak. Burros were used to pack building supplies, living supplies and equipment to the mountaintop. Most difficult of all to transport were the delicate recording machines and laboratory equipment. Even water had to be transported by burro until collection tanks could be built.

Harquahala was an observatory without telescopes. Rather, a theodolite was used for measuring the sun's altitude above the horizon. Pyrheliometers, mercury thermometers with shutters that opened or closed at set intervals to record heating and cooling, measured energy from both the sun's direct rays and scattered rays, and a pyranometer, an electric instrument, measured heat from the atmosphere around the sun. After tedious observation and data collection, the raw information was mathematically calculated by hand, sent to Washington, D.C., compared with data from another observatory, and used in forecasting weather.

ACCESS: To reach Harquahala Peak from Phoenix, take I-10 west to the Salome Road exit. Turn right and follow for 9.6 miles to Eagle Eye Road. Turn right and go 8.5 miles to the dirt road heading north. Or travel north on I-17 to the Carefree Highway, west to Highway 93 and north to Wickenberg. From Wickenberg, take Highway 60 west to Aguila, travel south on Eagle Eye Road 18.5 miles to the dirt road heading north. The road leading to the Observatory is 10.5 miles long in is very rugged and steep in places. Four-wheel-drive is required.

MAPS: Harquahala Peak Smithsonian Observatory is depicted on USGS 7.5-minute topographic map "Harquahala Mountain, Ariz."

NOTES:

  • Remnants of prospecting and mining lie near the Observatory and elsewhere in the Harquahala Mountains. Be aware of the danger these remains pose, and avoid them when exploring the area.
  • You may encounter rattlesnakes or other poisonous creatures; watch for them and be careful where you put your hands and feet. Do not harass reptiles - most bites result from people playing with, collecting or attempting to kill them.
  • Thunderstorms on Harquahala Peak are often violent and dangerous. Should stormy weather arise during your visit, leave the mountaintop as quickly as possible.
  • Please help preserve our cultural heritage. The Archaeological Resources Protection Act of 1979 makes destruction of sites a criminal offense. You can help by reporting the theft or destruction of cultural resources on public land. To report an incident, please contact Phoenix District Dispatch at (623) 580-5515, the La Paz County Sheriff at 669-2281, or the Maricopa County Sheriff at 256-1030. Protecting Arizona's history is everyone's responsibility.

 Hassayampa Field Office 
21605 N. 7th Avenue
Phoenix, AZ 85027-2929
Phone: (623) 580-5500
Fax: (623) 580-5580
Field Manager:  Rem Hawes
Hours:  7:30 a.m. – 4:15 p.m., M-F