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Human History and Geology

Human History

The landscape may seem bleak and forbidding but it contains all the essentials needed for survival in this harsh environment.  The forces of the geological composition provided springs for the earliest hunting and gathering native people that drifted through this area 5000 years ago foraging for the plants that sustained them.   The few nearby springs brought wildlife within ambush range of these people.   Two miles southeast of the peak is an area named Boulder Pass that an archeologist investigated in 1994.  The area had been used for hunting and food gathering for centuries before the Hohokam people arrived.  The Hohokam also used the area for their hunting grounds and began planting their crops on the edges of the arroyo.  The site was abandoned around 1225 A.D.

Spanish influence began in the 1500s and brought many changes to all the native people living in the region.  Livestock and new agricultural crops provided additional food and trade sources.

American settlers started to use the area in the 1800s for ranching and some mineral prospecting, but it was not until 1916 that E.O. Brown established a ranch within site of Pinnacle Peak.  Over the decades, the area has evolved from ranching into dude ranches to homesteads and cowboy restaurants.   Today residential developments surround the park.


Pinnacle Peak, jutting skyward 600 feet from the valley floor, is largely composed of granite.  The crystallization of slowly cooling molten rock deep in the Earth formed this granite over 1.4 billion years ago.  The natural forces of faulting, erosion, uplifting and deposition of overlaying rocks have uncovered this granite.  Some of the common minerals that have formed this granite are quartz, biotite mica, and feldspar.   The minerals formed an interlocking pattern as the magma cooled.  Water and ice, combined with the forces of gravity and the passage of time has decayed and removed some of the minerals, leaving it in the rounded boulder shapes you see today.