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2021 Map of Tassajara

Name: 2021 Topographic Map of Tassajara
Creator: U.S. Geological Survey
Published: 2021
License: https://creativecommons.org/publicdomain/mark/1.0/

USGS Topo · Published 2021

About this map

The Diablo Range dominates this landscape on the edge of the San Joaquin Valley, where the ridges of the Black Hills and steep drainages like Riggs Canyon transition into the eastern foothills. The small settlement of Tassajara sits at the junction of Finley Rd and Johnston Rd, serving as a focal point for a region defined by its canyons and historical ranch roads. This 2021 survey reveals a complex network of trails, including the Volvon Loop Trl and Eagle Trl, that traverse the high ground near Windy Point and Oyster Point.

Southward, the terrain opens into broader valleys such as Collier Canyon and Doolan Canyon, where the landscape is marked by the Contra Costa Co and Alameda Co boundary. Water sources like Sycamore Spring and the winding course of Marsh Cr indicate the natural hydrology that supported early grazing and settlement patterns in this part of the county before the suburban expansion of the wider East Bay reached these hills.