Mount Diablo Meridian and Base Line - Mt Diablo, CA
Posted by: Groundspeak Premium Member DougK
N 37° 52.901 W 121° 54.845
10S E 595495 N 4193243
This is the location of the Mount Diablo Meridian and Base Line for the PLSS within Northern California and Nevada.
Waymark Code: WMBMT4
Location: California, United States
Date Posted: 06/03/2011
Published By:Groundspeak Regular Member GEO*Trailblazer 1
Views: 17
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On a clear day from the top of Mount Diablo, one can see more land than anywhere else in the United States.

Because of its prominent position, Mount Diablo is the starting point for the establishment of land boundaries throughout most of Northern California and all of Nevada. The summit is the location of the "Initial Point," the north/south meridian, and east/west baseline intersection point that is the basis for most property boundaries.

Today, the summit of Mount Diablo is inside the Mount Diablo Summit Building. An exposed piece of rock, which is the summit of Mount Diablo (elevation 3,849 feet) is left unpaved for visitors to stand on. Next to this summit rock is a stone marker with a plaque that tells the history of Mt Diablo and the Public Land Survey System. The plaque reads:

THE MOUNT DIABLO
SURVEY MARKS

With its unobstructed view, Mount Diablo's summit has long been an important reference point for land surveys in the far west. In 1851, Col. Leander Ransom began subdividing the public lands by establishing the Mount Diablo Initial Point. From this point, lines were extended North, South, East and West forming a survey grid that covers most of Nothern California and all of Nevada. This point is marked by a rectangular depression in the exposed bedrock, three feet northeast from the center of this pillar. In 1852, R. D. Cutts of the Coast Survey established a different survey mark from which he began mapping the state's waterways and surrounding topography. This point is marked by a copper bolt inside the base of this pillar.

Plaque donated by:

Northern and Southern California sections of the
American Congress of Surveying and Mapping

Mount Diablo Surveyor Historical Society

East Bay, San Mateo/Santa Clara, Monterey Bay Chapters of the Northern California Land Surveyors Association

Northern California Surveyors Joint Apprenticeship Committee

Kearney Pattern Works and Foundry

Placed in 1993

The Summit Museum is open daily from 10AM-4PM.

Type of survey mark: Post with Marker

What indicators are near the mark to help people identify where it is located?:
Mt Diablo Museum Tower contains marker post.

What property is this mark defining?:
Prime Meridian for Northern California Base Line for Northern California and Nevada
Visit Instructions:
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