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1991 Map of Tassajara

Name: 1991 Topographic Map of Tassajara
Creator: U.S. Geological Survey
Published: 1995
License: https://creativecommons.org/publicdomain/mark/1.0/

USGS Topo · Published 1995

About this map

The Black Hills dominate this section of the Diablo Range, where the boundary between Contra Costa and Alameda counties follows the ridgelines and canyon floors. The landscape is defined by its educational and ranching history, evidenced by the presence of Tassajara Sch and Highland Sch, both marked as abandoned by the early 1990s. These former school sites sit near critical rural arteries like Tassajara Road and Highland Road, which historically connected the scattered homesteads of the interior valleys.

Creeks such as Marsh Creek and Cayetano Creek carve through the terrain, originating near summits like Oyster Pt and Windy Pt. A significant portion of the northern area is protected within Mount Diablo State Park, while the eastern reaches include the legacy of Spanish land grants such as the Las Positas Grant and Cañada de los Vaqueros. The map illustrates a transitional period for these canyons, where ancient land divisions meet modern conservation boundaries.