The Story Behind the Initial Point atop Mount Diablo

CCCHS Author in the Archives Series presents 

John Pettley, a professional land surveyor for over 38 years, talks about the significance of his amazing find in 1987. At the time, John was a surveying student at California State University at Fresno, and working on his senior thesis, when he made an important discovery about the history of the survey marks atop Mount Diablo.

On July 18, 1851, Col. Leander Ransom of the General Land Office (GLO) labored through thick brush, steep terrain, and harsh summer heat to establish the initial point on the highest rock at the summit of Mount Diablo in Contra Costa County. There he chiseled a hole in the rock and erected a pole with a large flag that could be seen for miles from the surrounding countryside. The grid lines intersected at the Initial Point on the summit of the mountain.

This mapping grid was extended to cover most of Northern California and all of Nevada and was used in deeds to describe the property boundaries in those areas. This system helped solve many land boundary disputes as property could be described in terms of a uniform starting point with officially surveyed lines. References to this system are found in numerous property deeds even to this day.

Step back in time with us as we hear the fascinating story of John’s journey in rediscovering this important piece of California and Nevada history!

Admission is FREE for CCCHS members, $10 for non-members. RSVP IS REQUESTED.

Reserve your seat and purchase tickets on Eventbrite.com. Questions? Please call (925) 229-1042 Tues-Thurs 9am-4pm or send an email to mkting@cocohistory.org.

- Doors open at 4:00 p.m. John’s talk begins at 4:30 p.m. 

- Beverages and snacks will be available for purchase at the Campbell Theater lobby bar.

- Complimentary waters provided by CCCHS

- Downtown parking is free on weekends.

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About the Speaker: John W. Pettley has been a professional land surveyor for 38 years. He received a Bachelor of Science degree in Surveying Engineering from California State University at Fresno in 1988, and a Bachelor of Arts degree in Geography from Cal Poly Humboldt in 1978.  His land surveying experience includes completing a wide variety of surveys and mapping projects for municipal and private sector clients.  He is currently employed by Greenwood and Moore, Inc., an engineering and surveying firm in Castro Valley, CA, and is also an active docent with Mount Diablo State Park where he educates visitors about the surveying importance of Mount Diablo. He is also a member of the Mount Diablo Surveyors Historical Society.

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‍All proceeds benefit the preservation work of the Contra Costa County Historical Society.‍